Attic Hatch Air Leakage and Heat Loss

If you have an attic and you get Ice Dams on your roof, chances are that your Attic’s Hatch is contributing to heat loss. Whether you have a regular hatch or a drop ladder/staircase, air leakage through the hatch can contribute to heat loss and drafty areas within your home.

Attic hatch air leakage

This photo was taken on a fall day with a Blower Door running to depressurize the home – it shows the inefficieny of the hatch to contain heat within the conditioned area of the home (cold attic air entering is shown via the blue colors). Under regular conditions (when the blower door is not running), heat from the home will migrate through the edges of the hatch and enter the attic, which in turn heats your attic increasing the chances for ice dams

Another way of thinking about this is that the homeowner is spending money to heat an area of the home that should be kept cold

The solution to this issue is to make a hatch that has both Air Sealing and Thermal qualities. We build hatches out of 1/4" plywood that sits on a 1.5"-2" tall 3/4" wide frame, this way the hatch trim can sit on the hatch opening trim and 'draw catch' clasps can compress the hatch against weather stripping. We recommend 4"-6" of rigid board insulation on the back side of the hatch - see photos below. Drop stairs can be treated the same way - just build the hatch so it sits directly above the stairs. 

ANOTHER IMPROVEMENT: If you want to add more insulation to your attic, add a plywood barricade around the frame (on the attic side) that extends approximately 20 inches up – effectively creating a “chimney” around your hatch in the attic. This way, you can add insulation up to the edge of the hatch and not have to worry about covering it up - since there is R20-R30 on the backside of the hatch, you’ll never have to drape fiberglass over it again!

These solutions will help mitigate heat loss into the attic, ice dams, increase comfort within the home, and lower energy bills during the heating season.