Insulating Cathedral Ceilings

Insulating Cathedral Ceilings

Insulating Cathedral Ceilings

Wednesday, October 3rd, 2012 by Christian Nelsen

Cathedral ceilings open vistas that flat ceilings just cant match. They became popular in the 1970s and 1980s and remain a desirable feature today. The dramatic views, however, have come at a cost. Because rafter widths limit the amount of insulation builders can install, these ceilings often waste energy and money.

Upgrading the insulation in a cathedral ceiling, however, is a challenge. If you look behind the drywall (or tongue and groove boards) on your cathedral ceiling, youre likely to find a thin layer of fiberglass bat insulation, perhaps a flimsy vent baffle, and an air channel designed to vent hot air from eave vents to ridge and gable vents. The fiberglass has probably degraded, due to moisture that has condensed on it over the years. In addition, the roof framing may show signs of rot and mold, which results from moist air leaking through openings in the ceiling, such as recessed lights or the joints in tongue and groove ceilings. This air has been condensing on the rafters, ridge board and decking, winter after winter.

Cathedral ceilings, vaulted ceilings, loft ceilings, and other sloped ceilings all have something in common. They are tough to insulate effectively.

What can be done?

The least invasive approach to improving the performance of a cathedral ceiling is to seal it, along with the rest of the room, to stop heat loss by air leakage. This entails removing recessed lights (you can replace them with surface-mount fixtures, such as track lights), and sealing every crack and joint you can find. Air leaks also occur at receptacles and switches, junction boxes, pendant fixtures, baseboards, windows and doors, pipes, ducts, and wires, and skylights.

Once you have removed fixtures from the ceiling, you will have to do some patching. This may be an opportunity to install a layer of rigid board insulation under the old ceiling, followed by new drywall.

We at Dr. Energy Saver Connecticut can help! Contact us today to schedule an appointment for us to come and take a look at your cathedral ceilings. We are the experienced home insulation and energy experts!

Adding more insulation

If an inspection reveals that your ceiling is not well insulated, you can opt to blow in an insulating fiber or inject foam insulation into the rafter bays. The preferred fiber insulation today is cellulose. Made from newsprint and treated to resist fire, cellulose is economical and effective. A technique called dense-packing allows cellulose insulation to double as both a conductive and convective insulator (air seal). Unlike fiberglass, through which air flows with relative ease, dense-packed cellulose resists air flow along with all the moisture and heat the air is often carrying.

When we dense-pack a cathedral ceiling, all penetrations and gaps are sealed off. The bottom of each rafter bay is blocked, typically with a piece of rigid board insulation snuggly fit to the opening defined by the rafters, wall plate and roof sheathing. This prevents the cellulose fibers from filling the soffits. We typically access the rafter bays at the top of the ceiling and run a blower hose into the bay. It often involves cutting holes in the drywall that can be easily patched laterwe dont want any leaks! The cellulose is blown in with enough pressure so it becomes packed in place and wont sag or settle for the life of the house.

We can also use injection foam insulation to insulate cathedral ceilings and other sloped roof assemblies that are difficult to get inside. Contractors have had success accessing the rafter bays from the roof. Two courses of shingles were carefully removed, and holes were bored for injecting the foam. The shingles were then replaced after filling the bays with foam insulation. Injection foam offers a triple benefit. It is a conductive and convection insulator and a vapor retarder.


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