Question: I'm not experienced at building, but I would like to build an energy-efficient house to keep the building costs down. What are do-it-yourself "pre-cut" houses and are they energy efficient? Answer: Pre-cut houses offer the greatest savings for the do-it-yourself builder. The materials for your house arrive at the building site as numbered, lettered or color-coded pieces. Many pre-cut houses come with instructional videotapes; others offer classes and toll-free numbers. You can have many of them under roof in less than a week.
There are many types of pre-cut house kits available: post and beam, conventional stud, circular and spherical, metal framing and log. The manufacturers offer many standard floor plans and styles from 1,000 to more than 3,000 square feet, or they can modify a kit for your floor plan.
Pre-cut house kits are energy efficient for several reasons. The parts are manufactured in a factory, so they are held to close tolerances. Since it is your house, you are usually more careful about sealing tiny cracks and gaps. This results in an airtight house.
By their basic design and construction method, some pre-cuts are extremely efficient. Heating and air-conditioning costs that are 25 percent to 40 percent lower than a conventional house are not unreasonable.
For example, with metal frame and post and beam pre-cut houses, you can add high levels of wall and attic insulation. By using thick super-insulated stress-skin panels on the outside of the post and beams, heat loss and heat gain are minimized. With metal frame houses, the heavy wall support beams provide plenty of space for super-insulation.
Circular and spherical houses are probably the most unique of all pre-cut houses. These shapes reduce air leakage from the wind. They also reduce the overall exterior wall area, so energy is conserved.
Since you will save a lot on your building costs, purchase quality, well-sealing windows and doors. Thermal pane windows with a low E coating and insulated steel doors with magnetic seals are effective. For summer comfort, install reflective foil under the roof rafters and provide for adequate soffit and ridge vent area in the attic.
When selecting and planning your house, consider its orientation on your lot. You should attempt to get the greatest percentage of windows on the east and south sides.
Closets and storage areas on exterior north and west walls help to block the winter cold and afternoon summer heat.
Question: How can I determine when it is time to recaulk my windows? I really don't feel much air leaking in my windows. _ C.F.
Answer: Even if you don't feel air leaking in, the caulk may not be good. Outdoor air can be leaking in and coming out through electrical outlets, small cracks, and around baseboards. The best way to check it is to probe at it with a small screwdriver or ice pick. If it seems hard and brittle and it breaks away easily in spots, you can be pretty sure it is leaky. Always chip out the old caulk first before recaulking.
Question: I don't understand why it's important to insulate a floor above a crawl space or basement or insulate under a slab. Seems like a waste of money because heat flows up, not down. _ T.K.
Answer: Heat flows equally in all directions _ up, down and horizontally. You feel more heat above a hot object because hot air is less dense and rises. In addition to reducing the heat loss through a floor, insulation keeps the floor materials warmer and you feel warmer. Nothing makes you feel chillier than cold feet. When you feel chilly, you often turn up the thermostat a little and this increases your monthly utility bills.
James Dulley is an engineer whose column on cutting utility bills appears twice a month. Questions can be addressed to James Dulley, Cut Your Utility Bills, St. Petersburg Times, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.