In a narrow sense, insulation is the material added to slow down the transfer of heat. In a broad sense, it is the entire process of making a home more comfortable and energy efficient, and includes caulking, weather stripping, and window insulation.
In a new building or addition insulation is automatically installed. But to make an existing house warmer in winter and cooler in the summer, you should evaluate how well your house conserves energy. Otherwise, you may launch into a complicated insulation project when less expensive or more effective projects should be done first.
How does a house lose precious heat in the winter and admit unwanted heat in the summer?
Mainly through holes, most of which escape notice because they are so obvious. An ordinary single-glaze window, for instance, may allow as much as 20 times more heat to escape than the wall that surrounds it, even though the wall is far larger than the window.
An uninsulated roof or ceiling may take a third of all the heat your house consumes.
Poorly sealed cracks around the foundation, sill, chimney, or siding can account for 10 percent of your heating, and a ¼-inch gap under a door is equivalent to a 3-inch square hole in your wall.
If your house has many such cracks and gaps, they can add up to a hole the size of a picture window.
Where should you begin? The best strategy is to start with projects that offer the highest long-range payback for the money and effort extended. The following list ranks heat robbers from the highest to the lowest.
Some items, such as insulating walls, may be more effective than their position on the list indicates. It is the expense of doing the improvement that makes it relatively inefficient.
- Weather stripping around doors and windows
- Caulking cracks
- Insulating windows and doors
- Insulating attics
- Insulating heating ducts
- Insulating floors or basement
- Insulating walls
Where To Insulate
After taking care of all the weather stripping and caulking, you can turn your attention to insulation. The basic principle of insulating a house is to surround the conditioned living space (occupied areas that are either heated or air-conditioned) with insulating material.
Generally, it is better to start at the top and work down until the entire living space is wrapped in a blanket, although there may be good reasons for changing this order. Some surfaces may be difficult to get to and others may be insulated enough already.
The type of construction is also a factor. A single-story home built on a cement slab can lose tremendous amounts of heat through the exposed perimeter if it is not insulated properly.
Remember, you do not have to insulate everything at once. You can do small amounts at a time. There is also the law of diminishing returns — The more your home is already insulated, the less monetary return on new insulation.
1. Attic and Roof. If the attic is not a living space, insulate your ceiling. This is an easy project that involves rolling out blankets insulation or blowing in loose-fill.
If the attic is a living area, insulate the ceilings and walls, as well as any attic floor under eaves. Some of these spaces are readily accessible, but others may be covered with interior finish walls or ceiling material.
Your choices then are to blow in loose-fill from the outside or strip off the finished wall or ceiling material and install blanket insulation.
Ceilings that are also roofs commonly lose heat, especially the type with exposed beams and attractive roof boards.
Once solution is to apply panels of rigid insulation to the insides of the roof boards.
Most types of insulation must then be covered with wallboard because they are flammable.
If the ceiling is too attractive to cover, install insulation on top of the roof.
This involves ripping off the roofing material, installing a vapor barrier and rigid panels over the roof sheathing, nailing ½-inch plywood over the sheathing, and re-roofing.
2. Exterior Walls and Windows. Insulating exterior walls is easy during new construction or remodeling, but is a major project in an existing house. Usually, loose insulation is blown into the stud cavities through holes that are drilled in the exterior wall and then plugged. Or rigid insulation is attached to the outside of the house and new siding is installed.
Realize that it does not do much good to insulate walls unless you do something about the windows first, even after they are caulked and weather stripped. Glass is a poor insulator — about R-1, compared with about R-4 for a wall that is not insulated and R-11 for a wall that is.
There are two options for insulating windows. One is to add another layer of glazing, either by replacing the windows with double-glazed units or by installing storm windows (or sheets of plastic) over them.
The other option is to cover the windows at night with movable insulation, such as multi-layered Mylar shades.
3. Walls Between Living Space and Unheated Space. These walls are often easier to insulate than exterior walls because one side is not finished. Just install blanket insulation between the exposed studs, with the vapor barrier toward the living space. If both sides of the wall are covered, blow in loose-fill insulation or strip off the finish on one side and install blanket insulation.
4. Exterior Floors. If a floor is cantilevered out beyond the downstairs wall, blow in insulation from the wall side of each joist cavity. Or strip off the soffit boards, install blanket insulation from the wall side of each joist cavity. Or strip off the soffit boards, install blanket insulation between the joists, and replace the boards.
5. Floors Over Unheated Areas. Floors over unheated crawl spaces and basements are fairly easy to insulate, although not very pleasant to do if the space is cramped. Install blanket insulation between the exposed joists, with the vapor barrier facing up.
Hold the blankets in place with wire clips, chicken wire, or netting improvised from fishing line or tie wire. It is also important to solve any moisture problems under the house.
6. Foundations and Basement Walls. Basements and heated crawl spaces can be insulated from the outside or from the inside. If the inside walls are already finished, or if excavating around the foundation is easy to do, the best method is to install rigid panels around the outside of the foundation.
These panels must cover the part of the basement wall that extends above the ground, in addition to whatever can be exposed by excavating. This is also the method that should be used fro insulating around concrete slabs.
If the basement walls have not been finished yet, they can be insulated from the inside with blanket insulation or rigid panels.