One of the questions we get asked a lot is:
what's the best insulation material to use in my a-frame home?
In this article, I’m going to answer this question once and for all.
I’m also going to give you one practical tip on saving time and money on the insulation works for your building.
First of all, A-frame houses are not different from any other house.
So what works for a regular home will work for an A-frame as well, and vice versa.
Second (and more important), when I hear this question I am a bit concerned about the intention behind the question itself.
The real question when it comes to energy losses
You have to keep in mind that what makes a “good home” is not only energy efficiency... a good home is also a healthy environment where to live, comfortable, and durable.
If all these benchmarks achieved, you also get energy efficiency.
In other words, energy efficiency is just a byproduct of a good build.
If you are looking for “the best insulation material” with the intent of making your house more energy-efficient, you have it wrong.
...or better, you are looking at just one of the many pieces of the puzzle, and spending all your money on that piece won’t help you to get the results you want.
So, here it is on a bumper sticker:
Spending all your money on insulation won’t make your house super energy-efficient.
Because the heat doesn’t just go out from the building shell (walls, roof, foundation).
As a matter of fact, the biggest cause of heat loss in a building are:
- the ventilation system;
- the windows;
- the other building components (roof, walls, foundation).
So, my warm recommendation here (pun intended) is to spend time looking at the ventilation system and at the windows before you look at the insulation material.
Energy losses from the ventilation system
To keep a healthy environment in the house, you should ventilate quite often.
Ventilate means taking new fresh air from the outside while pushing out from the house the same amount of exhausted air.
Now, if you look at the amount of air in play here, the Passivhaus standard (which is one of the most strict and efficient construction standards we have) sets that a healthy ventilation flow should be of at least 20m3/hour/person.
If we take this as a reference and we look at a 100m2 house with 4 occupants, we see that the air would change between 6 and 7 times in a day.
In other words, you would be throwing out the entire volume of the house in warm air 6-7 times per day.
...at this point I have to remind you that you paid to warm up that air!
Do you see the problem here?
This is why, since the 80s, we have ventilation units with heat recovery.
In these machines, the heat is extracted from the humid warm air going out and transferred to the dry and cold air coming from the outside.
Although I’m not a believer in anything with declared efficiency above 90%, these machines do a pretty impressive job at saving energy.
Unless you have free wood to burn (like me), here is the suggestion for you:
a ventilation unit with heat recovery should definitely be on the list of priorities for your new home.
Energy losses from windows
People like glazed surfaces.
If you look at photos of houses on Instagram you’ll see huge windows and glass facades.
They look stunning, yes… but they are energy suckers!
Now, while it is true that you can compensate the energy losses in the window with more insulation material on the ret of the house, this possibility is not endless.
So my suggestion here is:
use the best windows you can afford and keep the size down to a good-looking & functional minimum.
Not only this saves you money on the windows but it will also save you money on the insulation since you don’t have to overcompensate the massive heat loss from the gigantic glass facade.
The 5 factors for choosing insulation
Now we finally come to talk about the insulation material in the roof, walls, and foundation.
In the structure of Avrame kit homes, we can accommodate up to 300mm of insulation material.
When using polyurethane as insulation material, this is enough to build an R70+ structure. In metric system that would be U-value < 0.10 W/(m2K).
But polyurethane is just one of the options and, if you don’t need that high degree of insulation, you can choose to use other materials.
The selection of the insulation comes down to 5 factors:
Everyone wants to live in a healthy environment.
The best way to get this kind of result is to use construction materials that are natural.
However, with time, organic materials can spoil and begin to rot. This would cause the formation of toxic compounds and it would harm your health.
To avoid this, it is advisable to use non-organic (and non-toxic) materials in the inner layer of insulations (last 45mm, on the indoor side of the vapor barrier). There are special wools developed for this use.
Another solution is to use building paper (or other specific membranes) underneath the finishing layer, to keep the particles of insulation material from entering the living space.
Some people are really concerned about the environment and so they want to use natural insulation materials.
Examples: are animal wool, straw bails, hemp, cellulose…
Now, while this is great, you must know that the insulation property of those materials is generally way lower than standard glass wool or rock wool. Their price is also considerably higher.
So you’d be spending more money to get less energy efficiency, and you’d gain in eco-friendliness (but be careful… you’ll still end up needing more energy to heat!).
- Performance (thermal transmittance)
Whatever solution you choose, the insulation has to prevent heat loss.
The more performing insulation material is polyurethane.
Polyurethane performs about 30% better than the most performing construction wools.
This is a list of insulation materials ranked by performance:
- Glass wools, rock wools, polystyrene (EPS);
- Eco-friendly materials (sometimes much lower energy performance).
Price is something many are concerned about.
Insulation materials ranked by price would be something like this:
- Polystyrene (EPS);
- Glass wools and rock wools;
- Eco-friendly materials.
- Ease of installation
This is one thing that almost everyone overlooks!
Here are a couple of examples:
A) While EPS is the cheapest of all, to install it you need spray foam and you are going to need a lot of it!
So, in the end, using EPS is not that cheap after all.
B) Wooden-based eco-friendly materials are difficult to cut compared to traditional wool insulation. This results in enormous installation costs, on top of the already expensive material.
A practical tip
The practical tip to save time and money when it comes to insulation materials (and building in general, really) is this:
the price of the materials is meaningless!
You always shall account for the material installed where you need it… and installed correctly.
Before building, make sure you budget your construction in the right way (check the Budgeting Guide for that).
Customize your choice
In the end, the choice is up to you: what’s your priority?
Do you want to create a healthy indoor environment?
Do you want to be eco-friendly?
Do you want to lower your bills?
Do you want to minimize the cost of construction?
I would suggest you take time to look into all the options available and then make your decision, considering also you can combine insulation materials to get the best of two different types.
- you could use 250mm of polyurethane on the exterior part of the construction AND use eco-friendly wool (free of toxic particles) on the inner 45mm (on the indoor side of the vapor barrier);
- you could use cellulose or wool flakes in the floor slab… these types of insulation are perfect for flat surfaces ( cause it is horizontal and it won’t settle, not so good for walls because they tend to settle) AND regular glass wool in the rest of the house.
To keep in mind...
The insulation is not provided with the house kit, at least not with Avrame house kits.
At this point you should understand why:
- insulation is such a personal choice, depending on your preferences and on what you can truly afford;
- it would be pointless to spend a great deal of money on shipping something you have available in your local shop.
For all the rest, there is Avrame.
We are here to support your self-building journey every step of the way, starting from the very beginning with our Quickstart Guide.