Sunday, September 20, 2015

Using Air to Keep Air Out

New sign courtesy of neighbor Elba.
(All photos by author except where noted.)

Waiting for delivery of barn garage doors and insulation. 
Going into this major building project, I knew that what I didn’t know about construction could fill volumes. My eyes glazed over at the mention of R values. I was much more excited about design and textures and colors. (Don’t get me started on colors names—Lighthouse Red, Olde Copper, Moonlight Sonata.) R values were, well, just numbers.

But, nothing can inspire more than saving money, and that is what R values are all about. So I promised to boost my insulation intelligence quotient in time for the big game (the House). As detailed in the previous post, were are now at the Barn stage, refining our contracting knowledge and skills.

Every surface of a building presents an opportunity to keep air out/keep air in. In the instance of a windswept New Hampshire mountainside, most of the time the objective is keep cold out and warm in; the opposite would apply in Santa Fe, New Mexico, for example. Building materials such as gypsum board or metal act as thermal bridges and allow heat transfer, wasting energy.

Science guy that he is, Doug explained how insulation and R values work. Oddly (to me) air is a poor conductor of heat—and a great insulator. That’s why bulky Irish wool sweaters keep you warm as does layering clothing. The idea is to trap air and keep it from moving around. Heat can flow in one direction only—from warm space to a less warm one. (Technically, cold is the absence of heat.) Insulating materials usually depend on air for their ability to block air exchange—think Eskimo igloos, thatched roofs, or straw houses.

With R Values, the higher the number the better. R values are numerical expressions of a material’s ability to conduct heat. R = 1/U where U= the amount of heat that passes through a square foot of a material in an hour when the temperature difference on either side is one degree.

Consider the R values of these building materials (per inch thickness):
Brick                                                   = .8 (pretty pitiful)
Plywood                                             = .47 (even worse)

Versus insulation:
Closed cell cellulose spray foam        = 6 to 6.5
expanded polystyrene.                       = 6 to 8 (see April 8 post on SIPs)
Styrofoam                                           = 3.5 to 5.4
Loose cellulose                                   = 3.2 to 3.3
Fiberglass bats                                   = 3.1

What’s your favorite energy source—hydroelectric, solar, wind, geothermal, nuclear? Our pick is none of those. The best energy is the energy we don’t use. And so we are investing in insulation, lots of insulation in preparation for -20F snow days.

Rough electrical done. 
The barn has double-glazed LoE argon R 3.6 windows sealed with spray foam around the perimeter, Green Gaurd-taped seams, blown-in R 49 cellulose ceiling/attic, and R 21 batts in the walls. The concrete floor, built on 6 inches of crushed stone, has 2 inches of “blueboard” insulation. And, our saving grace to keep us warm working in the barn—the Enerzone 2.3 wood stove, which will consume locally sourced wood harvested by home-cooked meal-fueled manpower (with a chain saw assist). Meanwhile, I will be busy knitting wool hats and mittens. 
Enerzone photo courtesy  

P.S. The road to the road to Tug Mountain was paved this week by NH DOT in record time (compared to another state that starts in New). 2.5 miles in two days!

Smooth road in time for leaf peepers and winter.


  1. Oooh, I love it when you talk tech! :) I wanted to go put on a sweatshirt just reading about this!

    1. We're going to need lots more than a sweatshirt. Get out the polypro!