Many components come together to create a sealed envelope in construction, but the primary (and most vulnerable) component is the spray foam, or open/closed cell, insulation used to insulate and seal your home.
So, what exactly is the “building envelope”? It’s what separates the interior of the home from the exterior elements. In a sealed envelope, every area within this barrier becomes equivalent to conditioned space (yup, even your attic), because it’s within the barrier.
The advantages of a sealed home are increased energy savings; added strength to the structure of your home; and an acting barrier to stop the intrusion of air, moisture, mold, pollutants, and dust from entering your home.
About the vulnerability: Improperly sealed gaps will result in issues (notice we didn’t say “may”). The difference in temperature and humidity that intrudes from gaps, even as small as 1″ in diameter, meeting that of the conditioned air inside the “envelope” results in condensation, which provides a breeding ground for a variety of types of mildew and mold growth. These conditions pose known health hazards, as well as costly property damage.
As an HVAC contractor, we’re typically the first to identify these types of issues, having been called in to investigate sweating ductwork or grills, mildew/mold growth, warm spots, etc.
About the picture: We were very recently called in to investigate “sweating” ductwork in the wine room of a recently complete home (our installation). The equipment has been operating since mid-January, all through the peak season of the summer, with no issues, so there was an immediate flag that we were likely looking for a breach. Sure enough, our tech found this gaping hole. If you look closely at the bottom of the frame, you can see the cut out piece of insulation is laying there right by the hole. What would’ve taken literally minutes to properly patch and reseal will now also include replacing damaged ductwork (completely saturated). This instance was actually discovered before any extensive damage or health risks evolved, but we’ve seen far worse conditions result from much smaller breaches.
The sealed envelope is not a new trend in building, so it’s a shock to us that breaches like this still occur so frequently. Nearly all breaches we come across are the direct result of a careless or uninformed act, such as the one pictured, not due to an imperfection in the original application.
We hope this article will help prevent you from incurring unnecessary problems that so often result in costly damage (to health and/or structure). Ask people you trust for referrals when you need work done on your home, be sure that you’re hiring licensed and insured professionals, and don’t be afraid to ask questions beforehand.
And if you have a sealed home, don’t let anyone in your attic without discussing this issue!