Stefan Milkowski and his family care deeply about building structures that are functional, durable, and beautiful. So when the time came to design and build their own home in Alaska, they were intentional with every aspect of the project, including the insulation. Here is their unique story.
When my wife and I designed our house, we knew we wanted to use natural and non-toxic materials as much as possible. Years of working in mostly commercial construction had left me wary of common materials and ways of doing things, many of which seemed bad for the environment, bad for the worker, or both.
We wanted a house that was simple but comfortable and built to last. We wanted to build sustainably, which to us meant considering the embodied carbon footprint of materials and overall energy efficiency of the house and using full life-cycle thinking about materials and processes – for instance, how to reuse or recycle the house after its useful life. We also wanted a building process that was hands-on and enjoyable and that connected us to where we live.
The design we settled on was a story-and-a-half timber frame with a gable roof. For the foundation, we hired a local contractor to drive piles, using second-hand steel pipe and skipping concrete entirely. We felled most of the white spruce and Alaska birch trees for the timber frame and used locally sawn spruce for floor and roof framing and wall paneling. We built fixed windows around insulated glass units.
Choosing insulation was harder. Timber frames often use structural insulated panels attached to the exterior of the frame, which can almost eliminate thermal bridging. Using batt or loose-fill insulation essentially requires building a second wall outside of the frame to hold the insulation and siding but can be cheaper and allows more standard window and door framing.
We live in Fairbanks and wanted at least R30 in the walls and R40 in the roof and elevated floor. We also wanted to minimize thermal bridging and use only as much framing material as needed. We ended up using a lattice structure in the floor and roof and Larsen trusses on the walls. In the walls and roof, we used Havelock Wool Blown-In insulation. We chose blown-in because we knew that if we were careful, we’d be able to fill the lattice, the trusses, and around any window openings or other areas with irregular framing, all without any waste. Including shipping, the price per R-value was about the same as rigid foam. In the floor, where the lattice was mostly uninterrupted, we used mineral wool batts to save time and money.
We also decided to hand stuff the wool in the walls and roof. Our wall system doesn’t have sheathing – bracing is provided by the frame itself – and I didn’t love the idea of blowing behind mesh and then covering it with a weather barrier or blowing behind a weather barrier we couldn’t see through. Mostly I was concerned that blowing wouldn’t get wool into all the small spaces created by the truss framing. And I couldn’t figure out a simple way to blow in the roof lattice. We also didn’t have line power on-site, and using the blower available locally would have required renting a pair of decent-sized generators. Part of our goal was to have fun building our house. Blowing with the equipment available sounded loud, dusty, and mechanical; hand-stuffing sounded peaceful, quiet, and maybe even enjoyable. I pushed back against the assumption that one of the most important parts of building a house – insulating it well – should take only a day or two.
Hand-stuffing a large project was, I should note, not advised by anyone. When you try to build according to very specific values, you get used to ignoring advice. We got it done. But looking back, it was a lot of work. We used 77 bags of blown-in for our 900-square-foot house. Our process was to cut open a bag on a sheet of plywood on sawhorses and pick it apart by hand before placing it. At first, we calculated the volume of a few bays and weighed out the insulation to get the density right. After that we went by feel, which I came to think was as light as you could get it while still completely filling the space. My approach was to leave no space larger than a half-inch marble. We found, coming back the next day, that the wool continued to fluff itself, filling in any small gaps. We didn’t notice any settling, and scanning with an IR thermometer this winter hasn’t shown any signs of it, either.
On the roof, we worked from the peak down, stuffing both layers of the lattice, then folding our barrier over the top and stapling it to the framing. Two-by material between the barrier and sheathing allowed for ventilation. For the walls, we stapled up a couple feet of our weather barrier (Mento Plus can be used in walls without sheathing), placed the insulation, then stapled up a few more feet and placed more insulation.
Standing and picking the wool into contractor bags – the part a blower’s agitator can do mechanically – took longer than the insulating itself. Dust can be kicked up during installation so we wore masks when fluffing. The stuffing itself went reasonably quickly when it was clear sailing, but slowed down a lot under windows, around blocking, or at the top of the walls.
Going slow obviously costs more, if you’re paying others or if you value your time. And it puts you up against the weather pretty quickly. At least with timber frames, where the walls are built from the inside out and you aren’t weathered in until after you’ve insulated, it helps to insulate quickly. It took us more or less two full Alaska summers to get the frame up, the roof on, and the walls insulated and covered.
That said, we did have some fun times hand-stuffing – chatting or binging on podcasts – and that’s more than you can say about almost any other kind of insulation. The wool smells good and feels good on your hands. Using it is altogether far nicer than using mineral wool, fiberglass, cellulose, rigid foam or spray foam. More importantly, we have high-quality insulation that should perform well for a very long time.
Stefan Milkowski lives in Fairbanks, Alaska with his wife and daughter and does natural building through Wall Tent Woodworks.