Home Not Comfy? Don’t just blindly throw insulation at it!

“Reno” shows are all the rage, and why not–saving an existing house with lots of character can save money over building a new home.  However, there are some times when you just don’t know how an “upgrade” like insulation or an air barrier will work with the existing structure and materials of the home, especially when it comes to keeping the house healthy and mold-free for another 50-100 years.  

This video by expert builder Matt Risinger is a great example. He is consulting on a nearly 100 year old brick home in Fort Worth that is under renovation by a fellow builder.  Some of the original walls had a sort of rockwool insulation; some did not.  The interior formerly had mostly plaster walls.  It was clear that all of the original materials (brick, wood, rockwool, plaster) were highly vapor-permeable, meaning that rain on the outside and humidity on the inside did not get trapped in the walls, causing condensation and mold.  Since moisture moves from areas of higher moisture to lower moisture, you don’t want to impede this drying process in all directions and trap it.  These materials allowed moisture to dry out in both directions: toward the exterior and the interior, and hence the wall framing and sheathing was in great shape!  Many inexperienced contractors might try make “improvements” by adding new insulation and/or an air barrier.  But how would the old exterior and framing deal with it?  It’s an uncertainty, one that Matt was unable to determine, and therefore recommended that the homeowners forego insulation in some areas in order to keep the home durable and healthy, because he decided that durability trumped energy-efficiency in that scenario.

This is exactly the problem in some attics in the UK (check out our article).  Spray foam was installed to make the home more “comfortable” but after a short time, the rafters and underside of the roofs began to get wet, grow mold, and deteriorate.  Many of these homes were over 50 years old with original roof structure, but this one “upgrade” started to make them deteriorate quickly!  Upon investigation, it turns out there were several mistakes made by haphazardly installing spray foam in these attics.  For one, England is wet AND cold in the winter.  Cold on the outside and warm on the inside can lead to condensation on the inside when there’s gaps in insulation, or there’s not a vapor barrier (because air carries a lot of moisture with it), and/or the insulation is not thick enough for the climate.  These factors do not even touch the fact that most of the roofs were not surveyed properly for existing leaks, which must be repaired first (spray foam, especially open cell spray foam, is not meant to stop water from coming in).  What a tragedy for the homeowners of these historic homes!  Many had to get the foam removed, get their roofs repaired, and re-evaluate what type of insulation to install.

Similarly, anybody can be “sold” on a new product, whether it’s insulation or ventilation or air sealing, etc., by enthusiastic marketing and salespeople.  You don’t have to have an historic home to make a mistake, if you’re replacing any material with a different one than what was installed.  What is called for, is a view and consideration of the home as a system.  My parents, shortly after moving into their barndominium, decided to have insulation blown into the attic to increase comfort during the cool winters and hot summers.  Easy-peasy, call the insulation man, done!  However, soon they started to notice an accumulation of  white dust all over the home.  Dusting and vacuuming barely kept up with it.  It was not until we sealed the tiny cracks around the ceiling fan fixtures, HVAC vents and bath vents that we noticed a significant improvement, because air currents were carrying fine particulate dust from the new insulation from the attic into the home (see article here). This was not such a costly mistake, but since my father has COPD, it certainly did not help his condition.  

What can be done to minimize costly renovation mistakes?  Here are some tips:

• Consider the characteristics of the old building materials that preserved the home well, such as being air and vapor permeable.

• Do your homework on the 4 Control Layers and their order of importance.

• Consider that if you’re not replacing the whole system, replacing only one part of the system can have a big effect on the rest of the system.  Insulating a previously uninsulated old building completely changes the moisture balance. (another great video by ASIRI Designs)  

• Consider that the best thing to do may be resisting putting modern materials in your historic home, and instead investing in more efficient heating and cooling to compromise (which is what the Fort Worth owners were recommended by Matt Risinger). 

• Go to GreenBuildingAdvisor, which has tons of helpful articles, and especially their Q&A section, where homeowners like you post their questions about construction techniques and materials, to find answers.  

• BuildingScience.com is another great website for learning about construction methods, materials and the 4 control layers. 

• Visit other homes in your area that are similar to yours and have renovated, especially more than a year in, to see what has worked for them.

• Get contracts in writing to cover installation mistakes (or poor choices and ignorance) by the contractors.

Photo by Adam Bouse on Unsplash