Building a House






Home



Introduction

Layouts

Is a house expensive?

Security and privacy

Reducing noise

Earth covered house

Underground level

Decreasing building and heating costs

Cost comparison

Tips

QA

Example layout

Links



Home design tips

Choosing a mattress

Losing weight

Noisy neighbors


Introduction

Some of the most important thing to keep in mind when building a house are:

  • Does the location have utilities, like water, sewage, electricity and gas.

  • How far the location is from stores, offices, schools, ambulance, police.

  • The cost of the land.

  • The cost of building the house.

  • The cost of heating and cooling the house, cost which depends on the location's climate, on the building materials and on the layout of the levels.



Layouts

There are several main functional layouts.



Single floor, on the ground

The advantages are: excellent visual design potential, excellent functional access to the (back) yard from (near) the kitchen, low noise (because it has most obstacles in front of it), maximum privacy (because it has the lowest profile, hidden behind vegetation), great earthquake stability.

The disadvantages are: wasted space for hallways as more bedrooms are added, good security requires expensive glass for windows (likely 50% more than normal glass) or a tall (and possibly view-blocking) fence, more exposed to possible back ups from the sewer.



Single floor, on the ground, wrapped around an inner yard

In this layout, there is an inner yard which is walled all around, yard toward which all the windows and low security doors open.

The advantages are: excellent security (even without shatterproof windows), maximum privacy inside (because it has no windows toward the outside), excellent privacy outside (unless the neighboring houses raise above the yard wall), low noise (because only walls are exposed to the outside noise), excellent visual design potential (because all yard facing walls can be glass), excellent functional access to the inner yard from (near) the kitchen, great earthquake stability.

The disadvantages are: hides the view from the location (which is not a problem inside cities), confined space outside, wasted space for hallways as more bedrooms are added, blocks sunrise and sunset light from lighting the front porch (because the sun is low), more exposed to possible back ups from the sewer.



Single floor, on the ground, covered with earth, all perforations to the outside (like windows and doors) on single side of the house

A house covered with earth has several outstanding advantages: exceptional sound insulation from the outside noise, exceptional thermal behavior which means very low heating and cooling costs, excellent visual design potential because of the separation of the interior and exterior layouts.

The first advantage exists because mass (of earth) reduces noise.

The second advantage exists because earth has a high thermal mass, and the area of the windows is small.

The third advantage exists because no matter what the interior layout of the space is, the exterior layout doesn't have to follow in interior layout because the exterior will be filled with earth.

Sleeping would be at its best because of the lack of sound, the absence of light in the bedrooms, and the stable temperature.

Other advantages are: low noise (because it has most obstacles in front of it), maximum privacy (because it has the lowest profile, hidden behind vegetation), great earthquake stability.

The disadvantages are: good security requires expensive glass for windows (likely 50% more than normal glass) or a tall (and possibly view-blocking) fence, more exposed to possible back ups from the sewer, reduced functional access to the yard (because the entrance door must be on a very specific side of the house), cellphone communication may be possible only near windows.



Double floor, on the ground

The advantages are: excellent cost efficiency (for both building and heating), excellent space efficiency (minimum hallways space required), good visual design potential, excellent functional access to the (back) yard from (near) the kitchen.

The disadvantages are: more exposed to surrounding noise, top floor less is private, good security requires expensive glass for windows (likely 50% more than normal glass) or a tall (and possibly view-blocking) fence, more exposed to possible back ups from the sewer.



Single floor, suspended on pylons

The advantages are: excellent security (as long as no window is near the entrance stair and door), you can view farther (if there is anything interesting to view), the entrance stair can be outside (so it doesn't require heating), the space from under the house can be used for utility rooms and covered entertainment area (without increasing the house footprint), less exposed to flooding, less exposed to possible back ups from the sewer (since it's higher above it), the thermal insulation from the bottom can be accessed (if necessary).

The disadvantages are: more exposed to surrounding noise, top floor less is private, no easy access to the yard, exposed to people who would maliciously drill a whole through the floor (the repairs for the underfloor heating would be very difficult).



Is a house expensive?

Is a house more expensive than an apartment? For a similar usable space and finishes, no. There is nothing which is intrinsically more expensive for a house. However, the location of the house is.

A house is made expensive by the choices made by people. They want more land for a larger backyard, more bedrooms, more bathrooms, all sorts of utility rooms. They choose a layout which requires more built space for the same amount of usable space, like on-suit bathrooms and walk-in closets. They want to have space for entertaining guests, and space for visitors to stay in. These choices lead to a layout which forces the entire house layout to become less cost efficient.

More space requires more heating and more cleaning, so the house maintenance is also more expensive in money, time and energy spent.

There is also the issue of having to deal with all the subcontractors. Some of them might try to get from you a lot more money than their services are normally worth, so you could overpay for what you want / get. They do this in the hope that you don't know the market prices.

The bottom line is that if you want to build a palace, you will have to pay for its build and maintenance.



Security and privacy

Shatterproof glass: If a thief has easy access to windows, use security / shatterproof glass to dramatically improve the security; this kind of glass can easily cost 50% more than normal glass (with similar heat loss properties). Security glass does break, but doesn't fall from the frame unless great effort is applied. The level of provided security usually varies with the thickness of the protective plastic layer. Cracked security glass will stay in place, insulating the inside from the outside, for a few days until it will be replaced, which is especially good in the winter. There is also the option of installing a security film on existing windows, but it's far more secure to install security glass instead.

Bulletproof glass is a more secure option, but the price is many times higher than the price of normal glass. Bulletproof glass is much heavier than normal glass, and the thermal conductivity is high (which means a higher heat loss). An active security system, like an alarm, is useless if the thief is quick enough, or if a criminal targets the people inside.

As a side note, tempered glass provides safety because it breaks in small pieces, but not security because it falls easily out of the window frame.

Walled land: A tall wall around the entire land is good for security and privacy. However, this limits the view from the location (which is not a problem inside cities).

Windows: To minimize heat loss and noise getting through imperfect window installation and gasket wear, almost the entire windows area should be fixed (= not opening), with a few small windows that open for ventilation (and possibly escape in case of fire).

No curtains: For a ground floor house, it's possible to have privacy inside without sheer curtains by installing outside, somewhere in front of the windows, decorative panels / walls made of a material (like wood) which has many cutouts through which light passes. However, these will block more of the view than curtains do.



Reducing noise

The house should be standalone, that is, one which is not connected to a building where other people live.

A single, ground level house would be quieter than any other layout because it's surrounded by most obstacles (like other houses and vegetation). Also, it's easiest to (later) build walls around the yard, walls that capture most of the noise.

All (above ground) the perforations (windows, doors, and so on) should be on a single side, facing away from the closest / noisiest road. This requirement makes the layout space consuming, when several rooms with windows are needed.

If possible, place bedrooms away from known noise sources, like roads, on the side of the house which is opposite to the noise source. This is a particular concern when there are windows on the side of the road, through which noise can enter easily.

A bedroom should have a single wall common with the outside, the one with windows, its other walls should be inside the house, common with other rooms or hallways. Take into consideration if you can have a bedroom without windows, in particular surrounded by other rooms; this bedroom needs to have very good lighting (in terms of design, not intensity).

Obstacles of great mass are the best way to dramatically reduce environmental noise. Obviously, you can change the volume of any material to have a greater mass, but the usable mass depends on its affordability. Earth and concrete are good airborne noise (like speech) insulators. Rigid materials, like concrete and wood (think musical instruments), propagate impact noise (like footsteps or a hammer) with ease, so which material to use depends on the characteristics of the noise your house is subjected to. To make things even more complicated, there are impact noises that come from far away that behave like a mix of airborne and impact noises, like car traffic, music beats from a subwoofer, construction work that involves hitting or drilling the ground.

The density of the walls should be as high as possible. If the external walls are made of concrete, they should be at least 15 cm (6 in) thick; more than this is a waste of money.

If you want to avoid very low frequency noises from the outside, the house should be covered by a lot of earth.

A wall made of (hallow) bricks that has the same mass as a wall made of reinforced concrete is less capable to reduce environmental noise because of the holes in the brick, the mortar and the holes (between bricks) not filled with mortar are weak spots that noise can pass through with ease.

The house corners should be thick, solid blocks of reinforced concrete, each poured in one piece, because sound concentrates in the corners and you need as much mass as possible there. Don't fixate on this as it's a small influencing factor in the overall noise effect.

U-shaped houses may amplify sound inside the U, especially very low frequency sounds; this refers to sound coming from outside the house, from the direction of the top and sides of the U (not from the bottom of the U). If you want a U-shaped house, make sure that the width of the U is much larger than its depth.

External convex walls are reducing noise better than flat walls, but flat walls are better than concave walls. "Convex" means bulging outside, with the middle toward the noise source. "Concave" means receding inside, with the middle away from the noise source.

A wood house may creak for years, when the temperature changes most, especially at night.

Window overhangs (like balcony ceilings) reflect outside noise toward the inside of the house.

Thermally insulate the external walls (on the outside) with basaltic fiber to also get a bit of sound insulation for high frequencies. Polystyrene distorts sound, it doesn't have sound insulating properties.

To minimize noise getting through imperfect window installation and gasket wear, almost the entire windows area should be fixed (= not opening), with only a few small windows that open for ventilation (and escape in case of fire).

The more panes a window has, the higher the sound reduction it provides is, so use triple pane windows.

The exhaust of the cooking extractor fan should exit the house on the same side as the windows.

Artificial ventilation, like air conditioning, may cause a bass-like noise in the pipes. The same thing can happen with the refrigerator and water heater (pump).

Vibrating mechanical devices, like pumps and ventilators, may cause a bass-like noise.

No-freeze refrigerators make small crackling noises from time to time. If you want to avoid hearing these, especially if the refrigerator is in an open space, plan to have it encased in an almost fit-to-size space with a (sound insulated) door that you can keep open during the day.

Small rooms, like bathrooms, amplify the outside noise more than large rooms do. Hard wall finishings, like tile and parquet, further amplify the noise.

For good (room) acoustics, sound should be either absorbed or diffused, not reflected, by areas that are as large as possible. Straight, flat walls (including ceiling and floor) reflect and even echo sound, which makes sound unclear / distorted / muddy. Soft materials, like textile / felt, absorb and diffuse sound. Rigid materials, like stone, reflect sound. Acoustic drywall (instead of standard drywall) absorbs (high frequency) sound.

You might here some people advising you to plant vegetation to reduce the noise. Vegetation does not reduce noise, unless your problem is a bit of "woosh" made by small cars going by your house.

If you want to read more about the effect of (unwanted) sound / noise over humans, see noisy neighbors.

Is it possible to have trouble living in a house which is too quiet? You shouldn't have such a problem if you only block the outside noise from getting inside the house, but if you add heavy sound insulation inside the house then many people may have trouble adapting to such an quiet environment. If you think that your house is too quiet, you can add white noise.



Choosing a location

If you want to have quiet, the house should be away from large urban areas, from industrial areas, from busy roads, and should face away from such locations even if they are far away, because such locations may be sources of bass-like noise.

Move away from the city center, in the suburbs. The nearby area should have no business buildings, no hospitals, no schools, no parks, and no apartment buildings.

Try to find a location where people move voluntarily in order to get away from noise. A location with old houses, where people were born a long time ago, might be noisy because those people are like most people, that is, they are not seeking quiet locations on purpose.

If you want your home in a mountain area, make sure there are no nearby tracks for ATVs and dirt bikes; obviously, these could easily pop up later. Your property should be quite large so that your house could be as far as possible from such tracks.

Look for a standalone home, one which is not connected to a building where other people live.

The much smaller density of people, combined with the lack of connected walls, significantly reduces the probability of being disturbed by noise.



Earth covered house

The perfect sound insulation is achieved by being surrounded by the void of space (because void can't transmit sound), but that's not practical. The only remaining way to have true sound insulation is to be surrounded by an enormous mass of matter (like earth) which absorbs most noise.

Covering a house with earth is an attempt to obtain true sound insulation that creates a truly quiet home, not just to reduce the noise. This can help even in the case of severe environmental noise, but not if the ground itself is shaking (due to the use of nearby heavy machinery). This also insulates the outside from the noise inside, so a cinema / music room would produce little noise outside.

Covering a house with earth is, by far, the best sound insulation solution because: it's cheap, it's environmentally friendly, has no health risks (not more than the earth you're living on has), has no risk of faulty installation, and can scale easily to a larger mass (for more insulation). However, there are pest risks, like termites; termites don't like rammed earth because of its high density.

Since the roof is covered with earth, you can seed the earth with small vegetation (like grass and flowers), and make a stair / alley toward a terrace at the top.

You may hear from sound insulation experts about a technique called "decoupling". When covering a house with earth, decoupling can't work because the ceiling can't be decoupled from the inside of the house since it must support an enormous weight.

An advantage of covering the house with earth is that it doesn't require workers with special knowledge, just the average construction workers, and has no risk of failing to fulfill its insulating purpose due to faulty installation. For example, earth doesn't require special joining because it just fills all the available space, and cracks would have to go all the way through the earth walls in order to make it possible for noise to get to the inside.

There are two possibilities: build an underground level, or build a normal house which is then covered with earth. Covering a house with earth can be done by putting earth between the house itself and an external wall which surrounds the house.

The most practical way to do it is to put earth between the house itself and an external wall which surrounds the house, and on the roof.

There should be at least 2 meters / yards of earth between the external wall (or the air outside) and the house. The roof should be covered with at least 1 meter / yard of earth.

The house must have all the windows (and other perforations) on a single side / wall.

The sound insulation provided by this solution is somewhere between an unprotected house and an underground level. The limitation comes from the fact that the house is in the path of (above-ground) noise, and since the wall with windows is not covered (in order to have a view from the house), it remains directly exposed to some noise.

To help with this limitation you can build a normal house, and then add a wing which is fully covered by earth and with no windows. This wing can contain all the rooms that don't need a view outside, especially the rooms that are mostly used at night.

Here are a few things to keep in mind about the wing:

  • Can be built later (after the house).

  • Bedrooms don't really need windows because they are mostly used at night (when they have to be dark in order to improve sleep), so they can be inside the wing. Other rooms that don't need windows: media room, utility rooms. If you want to have a view from the bedroom, you have to ask yourself whether you want to prioritize the view over the quality of sleep (and the health improvements that sleep quality brings).

  • Since there are no windows, all the walls can be thermally insulated. This complete insulation combined with the fact that the earth will have virtually no temperature variation (unlike the air outside), means that the wing will have very little heat loss, so the thermal comfort will be very high.

  • The wing can be heated and cooled simply through the ventilation system, which means that the cost of the heating and cooling equipment is much lower. Also, the wall which is (now) free of windows is available for something else, like a projector screen, furniture, fancy design.

  • You can mount light panels on a wall to simulate daylight coming through translucent windows. You can cover the panels with thin, textured textile fabric, for design. Such panels can be stressful for the eyes, if they are too intense compared to the light from the rest of the room.

  • Is truly private since there are no windows. Doesn't need curtains.

  • Any room that you can move from the main house into the wing means a reduction in windows, heating and cooling costs (including equipment) for the entire house.

  • The wing (its floor slab and walls) has to be decoupled by the rest of the house, and connected with a narrow hallway. This would reduce the risk of fracture of the connected parts during an earthquake, and would stop the vibrations of the main house from being passed to the wing. The space in between the hallway and the wing should be about 20 cm (8 in) and filled with a non-rigid material, like extruded polystyrene (XPS).

  • The access hallway should be on a side of the house, and should end with a sound insulating door. The access door should not be in front of a bedroom door.

Can the wall with windows be insulated in any way? To some extent, yes. A walled yard can be created later; the yard walls must be at least as tall as the house (= top of the roof). The yard walls would absorb most of the noise coming toward the windows, but some of the noise will pass over the wall (the noise reduction would still be significant) because the noise source spreads the noise in all directions.

An advantage of an earth covered house is that only the shape of its external wall is visible from the outside, so its internal layout can be as functional as you need it, without affecting the external esthetics.

The external wall should not have protuberances that could trap sound waves, so its shape should be rectangular (for practical reasons); the ideal shape is circular.

The house must be on a single, ground level. Since the house is above the ground, the risks of water infiltration, flooding and sewer back ups are minimized.

The house must be made of thick reinforced concrete in order to support the weight of the earth, rain water and snow. The roof requires a concrete slab under the earth.

Earth density depends on composition, wetness and compactness, and is 1.2...2.0 tonnes / m3. Wet soil density is on the upper side of the range. Earth must have a density below 1.6 tonnes / m3 in order for vegetation to thrive on it.

Snow density is variable. Settled / old snow density is 0.2...0.3 tonnes / m3. Wet snow density is 0.4...0.8 tonnes / m3. Ice density is 0.8...0.9 tonnes / m3.

For the recommended height of 1 meter / yard of earth on the roof, for a temperate environment, the roof should be able to sustain 2.0...2.5 tonnes / m2, but this can change based on the exact density of the used soil and on the environment where the house is located.

The external wall should be at least 20 cm higher than the earth from the roof, so that the earth from the roof doesn't fly away in strong winds.

The external wall and the house should not be connected by anything rigid (which would transmit the impact noise from one wall to the other).

An advantage of an earth covered house is that the earth will provide a huge thermal mass, which will bring thermal comfort.

Of course, the external wall and the earth will cost money, but at the same time the heating and cooling costs (including equipment) are significantly reduced, and no curtains are needed.

Make sure the water is able to drain away from the house, but also from the earth, be it naturally (gravitational) or artificially.

The concrete roof should be sloped to allow water to drain naturally.

The walls and the roof (under the earth) of the house must be hydroinsulated. Since the concrete and the hydroinsulation don't allow moisture to pass from the inside of the house toward the earth, you can use expanded polystyrene for the thermoinsulation (which also doesn't allow moisture to pass through). The advantage of polystyrene is its resistance to moisture and extremely long lifetime.

The ventilation inside the house must be done with an artificial system, in particular for the rooms that have no windows.

Noise will be transmitted through the ventilation system (which has to open outside), so you should have a way to fully close the ventilation system, from the inside of the house.

Earth in a very large amount may completely block cellphone communication, and you may have signal only near windows.

Rammed earth density is around 2.0 tonnes / m3. Rammed earth is mechanically compacted earth, mixed with a small percentage of cement (like 6%). It's compacted on location within framework panels, so it's very labor intensive, and it has load bearing capacity. This is used in relatively dry climates to build house walls, although it can be covered with hydroinsulation.

Concrete density is 2.2...2.4 tonnes / m3. There is also a type of lightweight concrete whose density is below 1.9 tonnes / m3.

The Australian acoustic standard (AS/NZS 1276-19794) is one of a few which indicates the acoustic performance earth walls. It notes that a rammed earth wall with a 25 cm thickness reduces the sound with up to 50 dB, a 30 cm wall reduces the sound with up to 57 dB, good results for any material. Sound reduction is significantly lower for very low frequencies; see the "Estimation" section below.

A 15 cm thick wall of concrete reduces the sound with up to 52 dB, while a 20 cm wall reduces the sound with up to 58 dB.

There is no need to mechanically compact the earth as that would take an enormous amount of time and energy. The earth will compact on its own weight, in time. In fact, mechanically compacting the earth would make it more rigid and therefore less able to absorb impact noise.



Other materials

Would it be better to use only concrete instead of earth? Even if you ignore the higher cost, the answer is still no because concrete is a far more rigid material than earth, and rigid materials transmit impact noise with ease. Think at how concrete and earth sound when hit with a hammer: concrete noisily reverberates, while earth thuds. Very low frequency percussive sounds (like music beats and car traffic) act like a hammer (= impact noise), so they are transmitted easier through concrete than through earth. This is also why, when using earth filled walls, the internal and external walls must not be directly connected (by something rigid).

Would sand be a good choice? Because sand particles don't adhere to one another, sand would behave like a fluid during earthquakes, which would put great pressure on the walls holding it.



Noise estimation

While the sound volume reduction that you read in sales brochures of sound insulation panels may seem high, they are unlikely to be helpful to you.

If you need to build a sound insulated house, it's likely that you want to protect yourself from noise with very low frequencies, like that from music bass or car traffic.

Sound volume reduction is significantly lower for very low frequencies, than what you will see in sales brochures.

To approximate the sound volume reduction of a wall made from non-rigid materials, use: TL = 14.5 * log10( D * t * f ) - 26

Another source specifies: TL = 20 * log10( D * t * f ) - 48. The sound reduction calculated by this equation is higher than that of the equation above.

Factors: TL = transmission loss (dB), D = density (kg / m3), t = thickness of wall (m), f = frequency (Hz).

Unfortunately, I couldn't find an equation that includes the rigidity of the material. There is some some information but it doesn't add up. My guess is that happens because they don't handle beats, that is, pulsating sound.

This shows how inefficient it's to build a house in the path of (above-ground) noise, considering the effort that goes into covering the house with several meters of earth. However, this should be enough, unless in your case the noise source is very close and it's volume is extremely high, like rock concert-level music coming form a next door neighbor.

For example, for noise with a frequency of 10 Hz (the bottom of any normal subwoofer) and a 2 m thick wall made of soft earth (1200 kg / m3), you get about 38 dB.

To calculate the maximum acceptable sound volume just outside the house (ESV), based on the maximum acceptable sound volume inside the house (ISV), calculate ESV = TL + ISV. For ISV = 25 dB, you get ESV = 63 dB outside the house, so if the sound outside is louder than this, it starts to get stressful inside.

At the source, a subwoofer can exceed 100 dB, which is why you need either: a sound volume much lower than the maximum, a high distance from the noise source, an underground house (out of the path of the above-ground noise).

At the bottom of the frequency response, the ability of a subwoofer to produce a high volume sound reduces dramatically with frequency, in an approximately linearly manner. For example, a very expensive subwoofer that produces a sound volume of 100 dB at 20 Hz, can only produce 65 dB at 10 Hz.

The sound volume of a subwoofer is attenuated by air according to the distance from the subwoofer: V = SPL - 20 * log10( D ).

Factors: V = sound volume at distance D (dB), SPL = SPL rating of the subwoofer (dB, at a distance of 1 meter), D = distance from the subwoofer (m).

This means that every doubling of the distance reduces the volume with (only) 6 dB, which means that high-powered speakers / subwoofers that are turned to the maximum volume can be heard for many kilometers / miles, if there are no (heavy) obstacles in between.

Sources:



Bermed house

A bermed house is an earth covered house that has no external wall to hold the earth, but a long slope that props the earth which covers the house.

The slope's depth should be about 5 times the berm's height, because you don't want to have a mud slide in your yard.

For a town house, a berm takes too much space from the yard, while for a house outside the town is likely to be useless (because it's quiet anyway).

It may matter to you (or the city planners) that the house will almost entirely blend into a natural environment.



Underground level

An underground level built outside the footprint of the (above-ground) house, with only the entrance (with the stair) common with the house, has the following advantages:

  • Better sound insulation than a wing which is covered with earth, because it's outside of the path of the above-ground noise.

  • Can be built after the house since it's outside the footprint of the house.

  • Should the house fall, the corridor that leads to the entrance would be free of debris.

The biggest disadvantages of an underground level are the risk of back ups from the sewage system (if there is an underground bathroom), and the high risk of water infiltrations. Waste water pumps must be used for bathrooms and kitchen, but they require maintenance, and if one breaks down, well, you'll have to wait until it's fixed.

The entire shell of the underground level (walls, floor, ceiling) must be made of thick (reinforced) concrete, and must be hydro and thermo insulated on the outside.

The complicated part will be to build the stair from the house to the underground level, so that it's decoupled either from the house or from the underground level, yet fully integrated with the house.



Decreasing building and heating costs

One way to decrease the building and heating costs is by using multiple levels. Consider that the house is divided in the middle of the long side, resulting two halves that are 15 * 10 * 3 meters. Now imagine that these halves are put one over the other. At this point, the top and bottom sides of the house which are exposed to the temperature outside are halved; at the same time, the side walls which were inside the house, along the cut, are now exposed to the outside.

Since these side walls are much smaller than half of the top and bottom sides, it means that, for 2 levels, the house's area that's exposed to the outside has decreased significantly, which means a significantly lower thermal loss (which means a lower heating cost), but also significantly less construction materials for the outside (like insulation). However, the stair (1 + 1 m wide, 3 m long, 1 + 1 m landing area) will take some 20 m2 from the useful area of the house.

The smaller the house is, the smaller the cost saving is for 2 levels. This is because the gains provided by the area exposed to the outside by the top and bottom sides end up being nullified by the expenses caused by the area exposed to the outside by the side walls. On top of this, the stair eats a higher percentage from the useful space.

For a valid comparison, a double level house has to provide a layout which is just as functional as the layout of a single level house, for a similar gross internal area (= the area inside the exterior walls); the layout must account for the stair. Because the layout is critical for a cozy home and because it will vary a lot depending on preferences, a double level house could cost either less or more than a single level house.

The single level house takes twice the land footprint, compared to the double level house. However, if the single level house is raised on pylons (with one level), the space under it remains (partly) usable.

A house built on the ground usually has much less insulation under the floor than on the walls and roof, which means that it's losing several times more heat through the floor than through the walls. While the ground has a temperature that's a bit higher than the air's, so the heat loss is smaller than through the air, the difference is too small to matter. Make sure to insulate the bottom / floor as well as the roof and walls.



Cost comparison

Here are some simulations calculated for a medium-sized house located in a temperate climate. If you can build a program from source code, look for the "HouseBuildingCost" folder in the source code archive; you can see a screenshot from the program here.

The most important values are:

  • Building cost: This is your upfront investment in the house.

  • Building cost (money / gross m2): Same as "Building cost" but divided to the gross internal area (= the area inside the exterior walls).

  • Building + heating cost for lifetime: This is the overall cost that you have to pay for building the house and heating it for 40 years (the lifetime of the insulation). You can see that as the insulation gets better (with thickness), this cost first decreases and then increases. This means that using excessive insulation is not cost effective.

  • Building + heating cost for lifetime (money / gross m2): Same as "Building + heating cost for lifetime" but divided to the gross internal area (= the area inside the exterior walls). This is the default sorting criterion.

  • Building + heating cost for month: This is the cost above but divided to be paid by month.

  • Heating cost for average winter month: This is the cost to be paid monthly for heating the house.

Pay attention to the percentual distribution of the "House energy loss for average winter day". It makes sense to improve / increase the insulation for the area with the highest (heat loss distribution) percentage.

Since there is no prospect of having a cheap energy source in the next few decades, you can count on fuel prices to raise. Because of this, the used fuel price is higher with 50% than the current price.



Tips

The most efficient house shape is a cube because the cube has the minimum amount of (outer) area for a given volume, which means that it has the minimum area through which it loses heat.

Basaltic fiber and expanded polystyrene (EPS) can't sustain heavy weights, like poured concrete, while aerated concrete and extruded polystyrene (XPS) can. Because of this, basaltic fiber and EPS can't be used to insulate the bottom slab, while aerated concrete and XPS can. EPS may be usable as roof slab insulation (to keep the cost down), but it can't sustain anything more than the hydroinsulation; walking on such a roof must be limited.

Don't use flammable insulation, like polystyrene, on the inside of the house (like in the attic).

In locations with large temperature variations, don't use (spray) polyurethane or polyurea foam on roofs, for either thermal or hydro insulation, because it's likely to crack and allow water to sip in. This comes directly from people who have used it in a temperate climate, where there can be even 50 Celsius between summer maximum and winter minimum.



QA



How do I design the layout of my house?

First, design your home's layout, in a home design software, in 2D design only. Create your desired rooms as rectangles (or other shapes), of the desired dimensions, and then move them around until you get the layout you feel is best.

A simple drawing tool (like OpenOffice Draw) is enough for this, as long as it allows you to resize and rotate shapes / rectangles with the mouse.

Once this is done, you can move to a 3D design software like SweetHome 3D.



How do I start designing with SweetHome 3D?

See this QA.



Is concrete more polluting than brick?

You may have heard that concrete is more polluting than brick. Cement is indeed far more polluting than brick, but buildings are made with reinforced concrete, not with cement.

Concrete is made of aggregate filling (stone), cement and steel (for reinforcement). The aggregate filling is not polluting in comparison to cement and steel, and makes the largest part of the volume of the concrete. The production of steel / rebar used for reinforcing is highly polluting, but only a small amount is required (under 3%, by mass).

This means that concrete's pollution is averaged down by the aggregate filling, and, depending on the technologies used, it can have a level of pollution comparable to brick and even lower, but on average is a bit more polluting (like 20% more).



How do I reduce environmental pollution?

Reduce the size of the house, use proper thermal insulation, underfloor heating, and ceiling cooling.

Choose a layout which utilizes most of the built space, by reducing empty spaces like hallways, stairs and the middle of huge rooms.

Look into renewable construction materials, like rammed earth and wood.



How do I choose a mattress?

See this for details.



Example layout

We'll choose a simple example of a house that's 30 * 10 * 3 meters, with the long front wall facing the sun made only of glass / windows. The house is suspended off the ground, to simplify calculations; if the house is on the ground, the thermal loss is slightly smaller because the ground is warmer than air and it also stores the heat which comes from the house.

The house has a frame made of reinforced concrete. The top and bottom sides are made of 15 cm thick reinforced concrete. The outer walls are made of 25 cm thick hollow brick, and the thermal insulation is made of 20 cm thick basaltic fiber (installed on the outside of the walls, top and bottom sides). Concrete pylons keep the house off the ground (with one level).



Thermal performance

The thermal conductivity of a material, lambda (W / m / K), represents the amount of heat in Wh which is transmitted through 1 m2 of material that has a thickness of 1 m, during 1 hour, when the temperature difference between the material's internal and external surfaces is 1 C. The smaller lambda is, the better is the thermal insulation that the material provides.

The thermal transmittance of a material, U-value (W / m2 / K), is the heat loss per actual material thickness. Thermal transmittance = thermal conductivity / material thickness (m).

House thermal transmittance: HTT (W/K) = (Uw * Aw) + 2 * (Uf * Af) + (Ug * Ag)

House power loss: HPL (W) = HTT * (Ti - To)

Total energy loss for a month: TELM (kWh) = HPL * 24 (hours) * 30 (days) / 1000

Total heating cost for a month: THCM (money) = TELM * HFC

Legend:

  • U = thermal transmittance (W / m2 / K), A = area (m2), w = walls, f = floow / ceiling, g = windows.

  • T = temperature (C), i = inside the house, o = outside the house.

  • HFC = heating fuel cost per kWh (if you only know the price of gas per m3, just multiply that with 10).

Let's say that the brick is Porotherm 25 Robust which has a thermal conductivity lambda = 0.2 W/mK, and the thermal insulation is basaltic fiber Rockwool Frontrock which has a thermal conductivity lambda = 0.036 W/mK. We'll consider that the concrete has a thermal conductivity lambda = 2.3 W/mK.

Thermal conductivity for various materials: concrete 2.3, mortar 1.73, ground 1, solid brick 0.8, gypsum board 0.17, oak 0.17, hollow brick 0.14...0.25, pine 0.15, plywood 0.13, aerated concrete (AAC) 0.11, cork board 0.043, expanded polystyrene 0.039, basaltic fiber 0.036, extruded polystyrene 0.033, polyurethane foam 0.03, air 0.026, argon 0.016, krypton 0.009.

A brick wall has an effective thermal conductivity higher than the brick's value because a lot of mortar has to be used to hold the bricks together, mortar which has a very high thermal conductivity. For aerated concrete (AAC), very little mortar has to be used.

Should you use aerated concrete instead of brick? All things considered, since most of the area of the house is (insulated) concrete and glass, the differences between these materials are too small to matter, and it all comes down to how much it costs you per m2 (material and workmanship). There is no point in spending more money for one material, unless it gives you peace of mind to use that specific material. It's not important (from a heating point of view) if the walls are made with hollow brick or aerated concrete.

The difference could be made by something called thermal mass, that is, the capacity of a material to store heat (when heated), and to release it around it (when not heated anymore). As the thermal mass increases, so does the thermal comfort inside the house, especially in hot climates where it dampens extreme temperature swings (and therefore the cooling needs). Brick has a higher thermal mass than aerated concrete.

However, the large windows oriented toward the sun make this effect irrelevant since the heat from the sun quickly enters the house through the windows. Because of this, there has to be an overhang above the windows, overhang whose depth is calculated according to the location (which affects the sun's height above the horizon); this overhang is meant to block a significant part of the direct summer sun from entering through the windows, while fully allowing the winter sun to enter.

Disadvantages of aerated concrete:

  • Needs dry weather during installation.

  • Needs more care in choosing the screws used for hanging things on walls. Screws should be thin and very long, or special anchors should be used.



Calculating heating cost

Calculate the thermal transmittance of a layered system: U = 1 / (D1 / L1 + D2 / L2).

Legend:

  • U = thermal transmittance (W / m2 / K).

  • D = material thickness (m), L = thermal conductivity lambda (W/mK), 1 and 2 = layer number in the system.

For the insulation, we include a 10% thermal inefficiency, so we get 0.0396 W/mK.

The house uses brick or concrete, and basaltic fiber, so we have:

  • For the brick wall: U = 1 / (0.25 / 0.2 + 0.2 / 0.0396) = 0.159

  • For the concrete floor / ceiling: U = 1 / (0.15 / 2.3 + 0.2 / 0.0396) = 0.195

You can also use Ubakus to make the calculations.

For a highly insulating triple pane windows (with frame) we have Ug = 0.8 W/m2K.

For the natural gas price in the USA, we look for the residential prices here. We choose an average price of 10 dollars / thousand cubic feet, we means 10 / 28.3 = 0.35 dollars / m3, which is about 0.035 dollars / kWh (which, as it happens, is what I pay).

For the average winter temperature in the USA, we look here. We choose an average temperature of -5 Celsius (happens to be New York).

We have:

  • HTT = 0.159 * (30 + 2 * 10) * 3 + 2 * (0.195 * 30 * 10) + (0.8 * 30 * 3) = 213 W/K

  • HPL = 213 * (22 - -5) = 5751 W

  • TELM = 5751 * 24 * 30 / 1000 = 4141 kWh (for a month)

  • THCM = 4141 * 0.035 = 145 dollars (for an average winter month)

Keep in mind that this is the lowest price determined from simple calculations. The real price will be visibly higher because of installation inefficiencies and ventilation, but you can see the level of the heating cost.

Let's say that the house gets an average of 5 months of winter per year, and let's also say that the thermal insulation has to be redone every 40 years (or it will outlive you). The heating cost for this period is 145 * 5 * 40 = 29'000 dollars. To get the entire cost related to heating, add the cost for the thermal insulation (including the workmanship); the house's area that's covered by thermal insulation is 750 m2. You can then calculate the total for different thicknesses of the thermal insulation.

The heating cost is just one factor that matters. The other factor is the cost of creating the thermal insulating envelope of the house, because this is just a heating related costs that you have to pay upfront rather than monthly. This means that if you spend too much money on insulating the house, you can end up paying more on the house than you will spend on the heating fuel, for decades or even centuries.



Links

Techniques to reduce noise impact (U.S. Department of Transportation, Federal Highway Administration)

Noise control (Australia's guide to environmentally sustainable homes)

Rammed Earth Constructions

Eco Design Consultants







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