Sloped, vaulted ceiling design can be super energy efficient

Q. Is there any simple (do-it-yourself) method to remodel the ceiling in my bedroom or family room to a sloped, vaulted ceiling with skylights and beams? I also want it to keep my heating and cooling bills low. — H.J.

A. In many houses, you can easily convert your ordinary flat ceiling into an energy-efficient vaulted or cathedral ceiling yourself. With new super-energy-efficient skylights and the high open ceiling, your room will seem twice as spacious as before.

There are new super-insulated ventilated roof panels designed specifically for sloped ceilings without attics. These strong, easy-to-install panels have insulation values as high as R-40 and can be self-supporting.

Constructed with shiplap joints, these panels form a very airtight roofing system. Even with a large skylight, the overall energy-efficiency can be greater than a standard insulated flat ceiling/attic design. You will also feel more comfortable in your family room, especially during the summer.

Adequate roof ventilation is the key to building an efficient vaulted ceiling. These do-it-yourself roof panels are composed of a top layer of plywood or decking material, thick rigid foam insulation, and drywall or plywood on the bottom. Shingles are nailed directly to the top decking.

There are ventilation grooves in the thick rigid foam insulation beneath the decking. When this is bonded to the decking, the ventilation channels are formed. The drywall bonded to the bottom creates the ceiling surface in your room with the beams exposed below.

The grooves allow for air circulation immediately under the decking and shingles. With a special continuous roof ridge vent (made by several companies), air naturally circulates up through the roof above the insulation. This keeps it cooler in the summer and dryer in the winter.

Another construction method is to put insulation over the vaulted ceiling drywall. You can install special reflective insulation shields one inch under the roof decking. These hold blow-in insulation in place and create an air gap for ventilation. The reflective surface blocks the summer sun’s heat.

The amount of insulation you can install is limited by the depth of the rafters. You should install continuous ridge vents for adequate ventilation.

Select a super-high-efficiency skylight. At the very least, it should have low-e argon-gas filled glazing and a thermally-broken frame. This is the type of skylight I installed in my cathedral ceiling.

You can write to me for Utility Bills Update No. 481 listing manufacturers and product specifications of ventilated insulated roof panels, continuous roof ridge vents, super-high-efficiency skylights, and reflective insulation baffles, and schematic construction sketches. Please include $1.50 and a self-addressed business-size envelope. Send to James Dulley, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.

Q. What is a bio-gas generator and could we use one to produce energy for our home? I heard of their being used on farms to make natural gas. — T.R.

A. The most common bio-gas generator uses cow manure to produce methane gas. The gas is produced when organic material decays in a closed tank. The methane gas produced can be used just like natural gas in your home. The waste sludge can also be used as a fertilizer.

Unfortunately, it generally requires a fairly large unit (capacity to process the manure from 30-40 cows a day) to provide a reasonable payback on the investment. Unless you work on a farm, it usually isn’t feasible.

James Dulley studied energy management at the doctoral level at Harvard.