How To Turn Attic Into Conditioned Space

Fine homebuilding more musings of an energy nerd ventilation requirements in the covid era.

How to turn attic into conditioned space. The attic is fairly small at about 1 000 sqf total. Codes vary from place to place but the rule of 7 for using an attic as an actual room typically applies. Currently the attic is vented and has zero insulation anywhere. Open cell foam when properly installed with a vapor barrier should operate very similarly to closed cell foam.

That means you ll need 2x10 floor joists or maybe 2x8 in rare circumstances and at least 2x12 roof rafters. Moving the insulation layer from the attic floor to the sloped roof brings the attic into the home s conditioned envelope and greatly reduces the energy penalties associated with attic ductwork. Use closed cell foam insulation. Fortunately this is a fairly easy fix.

You can sister the joists by cutting 2 x8 boards the same length as the joists applying construction adhesive and affixing each to a joist with nails. The loss of conditioned air increases heating and cooling demand. However when open cell foam is installed without a vapor barrier which appears to occur often in real world applications the foam will absorb the water. Any water that leaks through the roof will pool on top of the vapor barrier and possibly next to the sheets of decking on the roof.

A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic. You might open up your attic and find bare joists with fiberglass or cellulose insulation between the joists. I m unsure of what to do and i m unsure of the most economical way to do it. At least half of your attic space must be 7 feet high by 7 feet wide with a total of 70 square feet.

Humid indoor air that escapes into the attic can condense on cold roof sheathing resulting in potential moisture problems. The attic space becomes indirectly conditioned as a result of the air leakage heat transfer and vapor diffusion through the ceiling. Pull down stairs won t work for an attic room so you must add a permanent staircase. That is it too will prevent moisture from penetrating into the attic area.

Warm air that escapes into the attic in winter can warm the roof deck and increase the risk of ice dams. Not addressed can lead to several problems.