Are you a homeowner or building manager?
Find a Contractor »

How to Air Seal an Attic “Right and Tight” – Part 1

Posted on:

When working to make a home more comfortable and energy efficient, simply adding more fiberglass batts or loose fill fiber in attics will not do the trick.  It is vitally important to air seal all the gaps, holes, cracks and other openings between the attic floor and the living space that the framers, electricians, plumbers and HVAC workers created when the home was built.  (And – the insulation contractor covers up with blown-in fiberglass or batts.)

Pipe and wire penetrations, can lights, chimney chases, top plates, drop down stairs and other gaps and cracks in the attic floor are places that the air your customers paid to heat in winter can leak into the attic. Since the attic is ventilated, this air is lost to the outside. Heat from super-hot attics in the summer can migrate into the home, increasing the cooling load in living spaces. Unsealed attic floors leads to rooms and homes that are uncomfortable and difficult to heat in winter and cool in summer.

At Attic Systems we follow these steps to ensure a properly air sealed attic floor:

1. Remove the existing insulation if possible – Attic insulation in a home can get pretty nasty. Over many years it collects dirt, dust, pollen, bugs, rodent feces, bird droppings and nests and other undesirable things. It’s possible that old insulation like this can be moved aside for a proper air sealing job that must be done prior to adding enough blown cellulose insulation, but removing it will make the job easier and you’ll be sure to find and seal all openings between the attic and living space.

Dirty, infested insulation

Plus, the air flowing through all these gaps and cracks deposits dirt and dust in fiberglass batts. Dirty insulation has a reduced ability to resist heat flow between the attic and conditioned areas in the home, increasing heating and cooling loads, and making people too hot in summer and too cold inwintertime.

Pipe Penetrations

2. Seal ALL gaps, cracks and openings – Carefully air seal the various points where air from the home leaks up into your attic and is lost. Use expanding foam, boards, caulk, and metal flashing and fire caulk around your masonry or metal chimney as appropriate. If necessary, baffles (air chutes) should be installed in each rafter bay to keep soffit vents clear and prepared for insulation.


Leaky Can Light

3. Install recessed can light covers, as needed – Recessed can lights are holes in the ceiling. Air leaks between the light fixture and the drywall, and through the fixture itself because of the many holes and seams in it. To make matters worse, when the light is on, incandescent and halogen bulbs burn at 380˚F and this hot air rises faster and causes the can light to leak faster.

Tite Shell ™ Can Light Covers

Fire proof can light covers should be installed over can light fixtures in the attic floor, fitted around wires and fixture struts, and sealed air tight with expanding foam.  Insulation can now be placed over these fixtures in the attic.


Leaky Kitchen Soffet






4. Fix any kitchen soffits or shower drop down ceilings – To have a comfortable, energy efficient home the ceiling drywall and insulation must be together. Sometimes the ceiling in a shower or a kitchen cabinet soffit are framed down lower than the rest of the ceiling. This leaves a big space over the shower or kitchen cabinets where air from adjoining wall and exterior stud wall cavities open to the vented attic via the soffit space can leak up into the attic. Often insulation is suspended well over the drywall instead of against it. To make matters worse, a can light fixture may be over the shower or in the kitchen soffit, causing more air to leak out of the home.

Seal off the top of the space above your shower with wood boards, foam boards and expandable foam sealant. Use can light covers over can light fixtures to isolate them inside a sealed space.

5. Build a storage deck and cat walk (if needed) – Many homeowners value attic storage space for appropriate items. But with blown insulation up to 17” deep, how can an attic still be used for storage? And if cooling or heating equipment is in the attic that needs to be accessed for service, how is this possible with a thick blanket of blown insulation on the attic floor?

SilverGlo™ SuperDeck

We use our exclusive SilverGlo™ board foam installed across the ceiling joists or existing plywood storage area. SilverGlo™ is EPS foam with graphite infused into the foam, which bumps up the insulation value by 24% over standard EPS foam. Then oriented strand board (OSB) is installed over the SilverGlo™ with very long screws and 3” washers. To keep blown insulation away from our new storage deck, we install dams made of OSB approximately 18” higher than the drywall ceiling.

Use a rigid foam board and the OSB dams to construct an 18” -24” wide, clean, useful, insulated cat walk to and in front of your heating/cooling equipment, separated from the blown insulation in your attic.

Uninsulated, Leak Pull Down Stairs

6. Install an air tight attic hatch cover – Homes with attic hatch pull down stairs leak a LOT of air that homeowners paid to heat to the vented attic, where it is lost. All this warm air leaving the top of the house is replaced with cold outside air entering at the lower levels of your home, causing drafts, cold floors and uncomfortable rooms that are hard to heat. In addition to these problems, your pull down stairs are a big area in your ceiling that is not insulated.

Attic System use our exclusive “David Lewis Hatch Cover™” that rests right over the pull down stairs. It stops air leakage and insulates over the stairs.  Made of lightweight SilverGlo™ foam insulation, it can be easily lifted aside to go up into your attic, and set it back in place when you leave.

David Lewis Hatch Cover

Some homes have scuttle holes to access the attic that have the same problem as drop down stairs; they leak a LOT of air!  The scuttle cover is weather-stripped to stop air leakage. Then the cover is insulated with a SilverGlo™ foam insulation panel.

Once all the attic is well air sealed, it’s time to blow in a thick blanket of cellulose.  We like to blow in 17” – 18” inches of TruSoft, our exclusive pest and mold resistant cellulose to provide an R-value of R60 – the best level of resistance to heat flow to and from the living area and the attic.

In part 2, we’ll discuss how to fix unusual or special problem building assemblies and other issues that you will find in attics; knee walls, multi-level ceilings, whole house fans, bath fans, ducts in attics and even mold!

Marc Tannenbaum

Posted In: Building Performance, Residential Buildings

Looking for an ACCA QA Accredited Contractor?

Are you a homeowner or building manager?


join now

PLUS It's Risk Free!