Home Energy Audit | Attic & Basement Insulation | Portland, Maine

Bungalow - energy audit

In December we performed an energy audit on this small, very nice home that really needs some weatherization attention. Recently moved in less than one year ago, the homeowners had already experienced high heating costs, drafty and inconsistent heating, and bad ice damming issues. With the inefficiencies we found they will also no doubt experience hot temperatures in the 2nd floor bedrooms this summer - all stemming from insufficient R Value (amount of insulation) and air leakage leading to devalued insulation.

This home really has all the classic tell-tale signs, and if they proceed with the recommended course(s) of action, they're looking at energy savings of easily 40% or more. (with an investment of $11-15K and paybacks less than 5 years!)

Basement Issues:

The vast majority of homes we see have this issue, even new construction - this thermal photo really drives home the ease of air leakage through this rim joist/sill plate location. The classic flow of air through a home is similar to that of a chimney; heat rises and exhausts through the top layer of the home and draws makeup air into the home (to balance pressure within the structure) with the largest air 'draw' or suction at the area furthest away...the basement. Therefore the basement is usually the location with the highest amount of air infiltration (see photo below).

Basement Rim Joist air leakage

The photo on the left shows the rim joist/sill plate at the top of the foundation wall. The thermal photo on the right shows how easily outdoor air is being drawn into the home. This ease of airflow transfer makes your heating system work harder as there is constantly new, cool air entering the building, it decreases comfort levels as the home constantly has 'cold spots' - as described by the homeowners, and it creates energy inefficiency as the air can easily move through the fiberglass insulation this home has in its walls and attic.

Attic Issues: 

As seen in the photo of the bungalow structure, the roof lines are similar to a cape style home - meaning the roofs eave-ends go down to the floor of the 2nd level of the structure. With soffit vents at those eave-ends, air is easily introduced into this home with absolutely NO airflow management once inside. The top right photo shows the knee wall cavity in the 2nd level of their home. Air is allowed to enter this cavity and move freely wherever it desires. 

Such as moving through the knee wall floor and into the livable areas of the home - middle right photo.

This airflow can also simply circulate within this knee wall cavity, enter & devalue the existing fiberglass batting - 2nd to last photo on the right. As we see the fiberglass is extremely dirty, to the point that the home owner and building inspector thought that it could be mold. In reality; it's just years of dirt! Fiberglass allows air to travel through it so easily that it traps years and years of filth just like an air filter in a car. When this occurs, severe devalued insulation ensues. Insulation like this works when it can retain or hold heat, with air running rampant within the fiberglass it washes all that heat away. So, how do we know this is true?...

...The bottom right photo shows the enclosed ceiling slope from the dormer side  of the bungalow. The eave-ends are vented and also have fiberglass batting insulation within them - and what do we see? The areas in blue are air moving into the vented soffits, up the rafter cavity and devaluing the insulation. The outdoor temperature was mild on this day, and we still see roughly a 13°  temperature differential. In a properly air sealed and insulated home this roof deck would be one solid color with no blue.

With devalued insulation heat has no effective thermal boundary to retain it within the thermal envelope, allowing that heat to easily conduct out. This air movement also creates increased pressure differentials on the home and forces, in a drafty home, air to enter and exit the home through various different avenues, ultimately leading to energy inefficiency, high energy bills, overworked heating systems, inconsistent and uncomfortable heating issues, and so on.

The Solutions:

  • Air seal and insulate the basement rim joist - 3" closed cell spray foam (install thermal paint per Maine Fire Code)
  • Remove ALL knee wall, enclosed slope, and attic fiberglass insulation - start fresh and clean
  • Air seal everything: any gaps, cracks, hole, or cavity that leads through to the attic, air seal accordingly: i.e. chimney chases, plumbing stacks, lights, bathroom fans, electrical wiring, etc
  • Properly air seal all eave end rafter cavities to retain proper insulation - i.e. 2" rigid board cut to size and foamed in place
  • Insulate roof deck from within knee wall: with either 2" rigid board strapped in place and dense pack cellulose within rafter cavity OR 5+" of closed cell spray foam to roof deck
  • Insulate all enclosed ceiling slopes with dense pack cellulose
  • Install R49 to attic flat with loose pack cellulose insulation

There are many other things that go along with solutions like this: combustion analytics, moisture management, and meticulous air sealing. Make sure you proceed with a professional energy audit prior to moving forward with solutions this extensive.