Building a House






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Introduction

Is a house expensive?

Reducing noise

Example layout

Decreasing building and heating costs

Cost comparison

Tips

QA





Home design tips

Choosing a mattress

Losing weight

Noisy neighbors


Introduction

One of the most important thing to keep in mind when building a house is the cost of heating and cooling it, cost which depends on the location's climate, on the building materials and on the layout of the levels.

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 sewage system.

  • Single floor, on the ground, wrapped around an inner garden. In this layout, there is an inner garden which is walled all around, garden 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 garden wall), low noise (because only walls are exposed to the outside noise), excellent visual design potential (because all garden facing walls can be glass), excellent functional access to the inner garden 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, more exposed to possible back ups from the sewage system.

  • 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 sewage system.

  • 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 sewage system (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).

Thermal insulation: 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 as well as the roof and walls.

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.

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.

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).

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).



Is a house expensive?

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

A house is made expensive by the choices made by people. They want more land for the garden, more bedrooms, more bathrooms, more space for all the 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 more restrained layout which forces the entire house layout to become less 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 when you want to build a palace, you will have to pay for its build and maintenance.



Reducing noise

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.

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

Obstacles of great density and mass (like compact ground) around the house are the best way to dramatically reduce environmental noise.

All the perforations (windows, doors, and so on) should be on a single side.

The density of the walls should be as high as possible, which means they should be made of concrete, not hollow brick or aerated concrete (AAC).

Artificial ventilation, like air conditioning, may cause a bass-like noise in the tubes.

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

Small rooms, like bathrooms, amplify the outside noise more than large rooms do.



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.

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.



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.



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.



Cost comparison

Here are some simulations calculated for a medium-sized house located in a temperate climate.

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.

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.



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 50 Celsius between summer maximum and winter minimum.



QA



How do I choose a mattress?

See this for details.



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, but on average is a bit more polluting (like 20% more).

If you want to reduce pollution then reduce the size of the house, use proper insulation, heating and cooling, and look into renewable materials (like wood). Alos, choose a layout which utilizes most of the built space, by reducing empty spaces like hallways, stairs and the middle of huge rooms.







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