Category Archives: 4. Components and Systems

Walls are only about 60% insulated.

Many of us have a mental model of insulation as the nice fluffy stuff sandwiched between the inner and outer layers of our walls. The (thermally) ugly reality is that most walls contain lots of doors and windows, and that the wall area that is not doors and windows is full of wood and steel.

Here is a sketch (thanks to my newly acquired skills in Google Sketchup) of a typical section of wall for my Park City house.

From the outside, the wall is:

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Optimal Insulation Strategy

My Park City Modern site is at 7000 ft. altitude,  is in climate zone 6, experiences 8196 heating-degree-days, and receives 340 inches of snow per year on average. Dealing with weather is a huge issue in designing for this site.

I will use natural gas as an energy source and wanted to minimize the use of that resource. As a result, I worked to build an energy efficient house that takes advantage of the winter sun. I also skipped the heated driveway, to my neighbors’ dismay.

My insulation plan is as follows:

Roof System

22 gauge cold-rolled corrugated roofing on

roofing felt with ice shield on the lowest 6′ of the roof on

ventilated nail base on

OSB decking on

Double 2×12 rafters 24 inches on center

Wall System

Foundation System

Flash and batt roof

Flash and batt walls

2″ XPS foam on outside of foundation walls

Fiberglass batts on interior of foundation walls
Some Comments

In order of priority, if you want to minimize heat loss, here is what you do:

Minimize windows

Minimize air infiltration

Minimize surface area

Maximize R-value

Minimize bridging through wood and steel structure

Most important insulation

Perimeter of concrete slab


Maximize winter solar gain

Condensation and Dew Point