How can I best improve the appearance and energy efficiency of my two story, uninsulated, balloon frame, asbestos sided home built in 1921?
A contractor is proposing removing the brittle asbestos/portland cement siding, blowing in cellulose insulation, applying house wrap and then vinyl siding. The walls have true 2"x4" studs with rough planks and tar paper under the asbestos siding.
I am glad you asked this before you got started.
Per the 2009 and 2012 codes your walls are required to either reach an R20 or you need to reach R13 with R5 continuous insulation installed outside. Blowing cellulose in at a 3.7 R value per inch gets you above the 13 but nowhere close to the 20 mark.
With this in mind and your desire to improve the energy efficiency of you house, everything above looks good but you should install rigid foam before you install the vinyl siding.
- To really help improve the efficiency and cut down on air leakage you might want to consider installing 2 - 1/2" sheets of foam offsetting the seams instead of just using 1 - 1" sheet.
- Along those lines make sure you pay close attention to your flashing details & air sealing.
I do have one additional word of warning and that is to make sure you don't have any old knob and tube still running in these walls and if you do, get that corrected first.
For more information:
Read "We have inadequate wall insulation. What is the best approach to insulate our walls?" a Q&A answered by Michael Holcomb.