Ice Dams, Mold and Insulation

“I think the City should offer incentives to create more energy-efficient structures, not inadvertently dis-incentivize them….I think we have to elevate the game significantly.” — Tim Eian

Q: Why do you think it is hard to get older codes updated for newer materials?

Tim Eian: Like politics, the building construction process is partially informed by lobbyists who want their products, and their systems, to remain the same.

One example for this in recent history in our practice are flexible tubes for ventilation systems, which are typically compared to the prevalent sheet metal ducts by inspectors. In the real world, the flex tubes offer many practical and performance advantages, but they do not fit the mold of the conventional and traditional duct work product.

Many inspectors realize that these conventional materials don’t do as good a job as newer materials, such as the flex tubes, but they are code legal. What are they going to do? Risk themselves by allowing an alternate?

Same thing with the use of fiberglass insulation. It’s a terrible product in terms of mold issues. Its R-value can decrease the greater the temperature variation between warm inside and cold outside due to convective currents inside wall cavities. And, in Minnesota, where we have such a wide range between indoor and outdoor temperatures, particularly in the winter, it makes no sense to use a product with decreased performance when we need it most.

Of course, it’s hard to make changes to products that have strong roots in Minnesota industry and manufacturing.

Editor’s Resources About Insulation

  1. Here is an interesting blog in 2012 by home inspector Rueben Saltzman about spray-foam insulation being used to create ‘hot roofs.’Insulation options
  2. An insulation expert at the Eco-Experience at the 2015 Minnesota State Fair (image of exhibit above) indicated that fiberglass is the weaker link in product choices, because it doesn’t wrap around ventilation pipes and other structures well, so leaks are hard to avoid, and it does tend to have mold issues. But it does tend to be the option of choice for do-it-yourself projects because it is easier to install.
  3. This is a great guide to insulation insights from the Environmental Protection Agency.
As I’m learning in the Q&A series with designers, integration of ventilation — to deal with moisture/mold issues — alongside tighter insulation options to reduce ice dam issues in Minnesota winters with air-leaky homes, is a science that requires intelligent input from those who understand building science well.

GreenDoctors says this about insulation options:

  • Cellulose provides good value and performance for the price. Cellulose is much denser and does a much better job at air sealing.
  • Closed cell foam provides exemplary air sealing and a high R value of 6.5/inch.
  • We are not in favor of fiberglass (except on the kneewall). We have observed many attics with the thermal camera and could see enormous amounts of energy percolating up through the fiberglass. Fiberglass also has this unfortunate property of losing substantial r-value when it gets cold outside due to the convective air currents that pass through it. The colder it is outside the more air pressure from the house pushing air through the insulation.

After testing various materials we determined that cellulose and closed cell foam performs the best, although we do use fiberglass that is sealed with building wrap on the kneewalls.

The Minnesota Building Performance Association says this about R-value (temperature resistance):

If you have an older home, built when insulation didn’t exist or wasn’t very effective, R-3 wall insulation was common. Today code-built homes have R-15 to R-21, and super-insulated homes may have R-60!… It’s very important to keep in mind that insulation is only one aspect of your heating/cooling puzzle.

Drafty windows, a failing furnace/air conditioner or other systemic issues could be at fault instead. How can you know the true causes?

Before you spend money on possibly the wrong solution, hire a Certified Energy Professional to effectively diagnose the problem. The Energy Pro will run tests to understand how leaky your home is, locate the air leaks, evaluate windows/furnace/air conditioner and existing insulation. The result is a “scope of work” plan prioritizing recommended work and defining what type of contractor to hire.