Did you know that our homes have roughly double the total effective insulation of the typical home in Austin? Why do we spend so much extra time & money on the insulation in our homes? The short answer is that it’s the right way to build, but here are a few specific benefits that we focus on:
1. Thermal Comfort: Thanks to this extra insulation you’ll be able to comfortably walk around our homes in whatever your most comfortable at-home in-rest attire is, whetherit’s during the peak of the hottest days of summer or the depths of the coldest morning in winter. Your home should be your sacred space, your recharge zone, your protective cave. A key to allowing for that experience is to have the home be thermally comfortable in whatever attire makes you feel good and a great layer of insulation all around the home is the way to get there.
2. Quiet: The thick layer of insulation around the home greatly reduces the amount of outside noise so that you can get a great night’s sleep or an even better mid-day nap. Similar to the note above on thermal-comfort, we have other tricks that we use to reduce exterior noise that we detail in other notes, but insulation is a significant part of the story.
3. Lower utility bills: Some likely the lower bills simply for the cash savings, others becauseit means they’re having a smaller impact on the environment, we like it equally for both reasons. The core energy needs of our homes are roughly half of the typical similarly sized home in Austin. It’s important to note that this reduction in your energy bill assumes that you have the AC cranking all summer and the heat on high all winter. You’ll be even more comfortable than in your old while also enjoying much lower utility bills. That’s the beauty of a well-insulated home.
In the heading we refer to one of the all-time most loved Austin-based companies, Yeti. We all know how great their mugs and coolers are at keeping everything the perfect temperature. They achieve this by super insulating their products just like we do ours.
A Brief History of Home Insulation
Insulation 1.0: The first homes in Texas had no insulation at all.
They just had a thin layer of wood at the roof and the walls. This design didn’t do much more than keeping out most rain and wind. The effective insulation level of these walls are R-1, similar to a single-pane of glass in a window.
Insulation 2.0: Eventually builder’s added insulation into the gap in the wood studs that provide the structural support for the home and also added another layer of wood over those studs as the interior finish surface.
This insulation was locally sourced items such as saw dust, wood shavings, shredded newspapers, cotton, and horsehair. This insulation was a great improvement and achieved an effective R-value of 6.3 but there were three big issues:
- Lower Thermal Resistance Per Inch: This material ranged in how much insulation it provided but it was all on the order of R-1.5 per inch, roughly half of the level provided by the insulation that is typically used in homes today.
- Not Enough: The thickness of the insulation was limited by the depth of the wood studs in the wall. Typical homes are framed with 2x4s so you’re only able to put 3-1/2” of insulation in them; not enough to achieve the goal of a thermally comfortable home.
- Thermal Bridge: Since the insulation was installed only within the wood studs that support the home, there was no insulation where the wood studs were located themselves. Anywhere there is a gap in insulation we call it a “Thermal Bridge”. Thermal Bridges are like super-highways for heat and noise. Both flow through them unimpeded and they create a dramatic reduction in your effective insulation in the home.
Insulation 3.0: There are a few improvements that builders implemented starting around the 1950’s:
- Better Insulation: Companies began creating different insulation products that provided more thermal resistance per inch such as Fiberglass, Cellulose and Open-Cell Spray Foam at roughly R-3.7/inch and Closed-Cell at roughly R-6/inch. Our preference is to use Cellulose in the walls where it does a great job of sound deadening as well and fiberglass batts in the ceiling where the Cellulose would sag too much over time. A few notes on Spray Foam. Many people happily live in homes with spray foam but I will never use this product inside my homes and I will never live in a home that has Spray Foam. My good friends at 457 High Performance Building Supply have done an excellent job explaining potential issues with spray foam insulation so please check them out for a detailed explanation here. My quick summary is that this material has the potential to off-gas some nasty chemicals into your home and the blowing agents used to install this materialcan have very high global warming potential.
- 2x6 Studs: You get over 50% more insulation in the wall by using 2x6 wood studs instead of 2x4 wood studs. We use 2x6s in all of our homes but it does not properly deal with the problem of the thermal bridge. A 2x6 wall with Fiberglass has an effective R-value of 19.9.
- Less Wood Studs: Another strategy is to build the homes with less wood studs in the wallsby placing the studs 24” on center instead of the typical 16” on center. Less wood studs means more insulation and less thermal bridges. This is an excellent strategy and we build this into our homes whenever possible, however, it can be difficult to do this perfectly on the two-story and three-story homes that we build. This wall with Fiberglass has an effective R-value of 20.5.
Insulation 4.0: A Honed Home with extra insulation and reduced thermal bridges.
At the walls we add a horizontal 2x2 so that there is a 7” thick cavity and we fill that entire space with Cellulose for an effective R-value of 27.4. At the roof we use 2x12 studs 24” oc filled with fiberglass batts and then outside of the roof sheathing we have a 1.5” layer of PolyISO foam insulation for a total effective R-value of 45.6.
A key reason we like this insulation strategy at both the walls and the roof is that it dramatically decreases the thermal bridges in these walls. Reducing the thermal bridge is important because it allows for more insulation in the wall but also because the thermal bridges are the locations where walls can form moisture issues. We use thicker insulation at the roof partially because we can, it’s much easier to have thick foam insulation on the roof than on the walls, and partially because the roof needs it, more heat generally flows through the roof per square foot than through the walls.
It's worth nothing that when we built homes up North we used two other methods, that were better suited to that colder climate:
- Double Stud Walls: There are many versions but ours had a 2x4 stud, then a 3-1/2” gap and then another 2x4 stud. This resulted in 10-1/2” of insulation in the walls, 3-1/2” of which was continuous with no studs in it.
- Thicker Exterior Insulation: We also had some homes that had 2” or even 3” of continuous foam insulation on the exterior of the woods studs.
Insulation 5.0: Next Steps
We can always insulate better and we’re always searching for new and improved methods. The main element that we are focused on right now is to get a good layer of insulation on the outside of all of our concrete foundations. When we built in colder climates like Philadelphia & New York our homes essentially sat in a foam insulation bath tub. However, for a few reasons we can’t build this way in Austin:
- Don’t Want Insulation Below the Home: It’s so hot most of the year that our homes actually benefit from being thermally connected to the soil below the concrete. Basically, the soil cools the home down a bit and prevents us from having to run our air conditioning so much.
- Our homes don’t have basements. Doing continuous insulation is much easier when you have a basement but in Austin we have a cultural preference for no basements plus much of our soil is either solid limestone or super-thick clay, both of which make it very difficult and expensive to build basements for smaller infill residential homes that we focus on.
With that said, we really should be insulating the sides of our concrete slabs where it is exposed to the air and include this in the whole insulation bubble around the home. There are solutions but not all building inspectors accept these solutions yet so each project we have to review it with them and get their approval. Nonetheless, we are working on some strategies to cover this last final section of the home so that the entire home is properly covered in insulation and we’ll keep y’all updated as we progress on this.
