How much Insulation Do I Need in my house build?
by Ian Thompson Editor
In this short video that lasts just two minutes, Matt Risinger and Steve Baczek discuss the correct amount of insulation for buildings in their native USA. The advice they provide could also serve as a basic guide for countries where building codes do not adequately address insulation. Surprisingly, many countries still do not insulate their buildings sufficiently.
When I design a house, I aim to make the walls as at least 300mm think to give me ample room for my insulation and services to coexist, not fight each other for room. I also try to use the best performing insulation my budget allows. Why? Because investing in good, sustainable, and healthy insulation is not only beneficial – for me it’s essential! Also, I personally find that thick exterior walls look better. They also provide me with the room to recess my windows and doors – a design feature I am particularly fond of.
In my opinion, proper insulation of your building’s exterior walls, roof, and floor, also known as the building envelope, is the most effective way to improve comfort all year round. It doesn’t make sense to invest in a luxury kitchen, high-end fixtures, and fancy furniture if your house is too hot in the summer or too cold in the winter. It’s important to get the basics right first.
Unfortunately, we still see houses being built with either no insulation, not enough insulation, or insulation that is paired with single-glazed windows and doors. My advice? Invest in a properly designed building envelope from the start of your build. This decision will likely influence your choices for wall, flooring, and roof building systems.
Remember to do your research thoroughly. Look at as many different types of insulation as you can. Don’t be swayed by sales pitches. Instead, trust in test results and the composition of materials. Some commonly available types of insulation can be harmful if not properly contained. Many are also not produced using sustainable and energy-efficient methods which I feel is also a feel-good factor. I personally prefer natural and some recycled products. Don’t forget to shop around – there are deals to be found.
Another related video from Steve:
How much Insulation Do I Need? Expert advice.
On the Build Show today, we’re answering the question: How much insulation is the right amount? I’m visiting with my friend Steve, a fantastic architect known for his high-performance work. Steve, how do you answer that question, how much insulation for my house?
The simplest initial answer to that question is, as much as you can afford. You can never benefit from too much insulation. That’s right. One of the things that I start out with is Building Science Corporation’s 10-20-40-60-5 rule. It suggests 10 for the sub-slab, 20 for the foundation walls, 40 for above-grade walls, 60 for the roof, and 5 for the windows. That’s where the insulation curve starts to flatten out. It’s a tipping point where the insulation, for the amount of money spent, makes financial sense.
Typically, here we’re used to 2×4 wall framing 24 inches on center. But I limit thermal bridging by using an R9 ZIP panel on the outside to achieve a continuous blanket of insulation. The windows have an R6 to R7 rating, depending on whether they’re fixed or operable. The walls come in at around the 40s in terms of R-value. I prefer the 2×8 framing for a single-framed wall, avoiding a double wall assembly. We have California corners where insulation is placed into the pockets to create warm corners on the headers. Instead of insulating between laminations, I size the headers as a uniform height and push them all the way to the exterior, creating a header pocket. Our insulator then insulates the header pocket like a cavity, although slightly shallower. With the continuous blanket of ZIP sheathing on the outside, as well as the R9 panel running around the whole house, it provides a complete thermal envelope.
To summarize, the R-values for this project range from R10 for the sub-slab, R20 for the basement walls, R40 for the above-grade walls, R60 for the roof, and R5 for the windows. Steve, good stuff! I’ll have a link to Steve’s website in the description below, as well as a link to the Building Science Corporation paper he mentioned. Otherwise, follow me on Twitter and Instagram. We’ll see you next time on the Build Show.