Because a large volume of indoor heat is lost through the ceiling, the attic floor above is considered the most important area in the house to insulate for winter comfort and efficiency.
Arguably the most important space in the home to insulate is the attic. This is primarily because heat naturally rises, which means that the attic will hold a lot of the heat generated in the home. During the winter, having that heat escape through the attic will push up energy bills.
In addition to walls and attics, insulation should be installed in ceilings with unheated spaces, basement walls, floors above vented crawl spaces, cathedral ceilings, floors over unheated garages or porches, knee walls, and in between interior walls—especially bathrooms—as well as ceilings and floors.
As for attic vs. wall insulation, always go for the attic. The largest pay back will be seen here. You would stop heat loss from natural convection and block solar gain (an increase in heat) in the attic, which can result in energy savings of 30 to 50 percent.
If You Must Choose Between One or The Other
If you must absolutely choose between attic insulation, wall insulation, or crawl space insulation, however, you usually will treat any structure from the top to the bottom, in that order because heat rises and the heating costs generally are more than the cooling costs.
Because of the indoor air quality and drafts, we recommend the crawl space be air sealed too. Air sealing and insulating your crawl space properly will improve the health of your home. It will also improve the energy efficiency, thereby lowering your utility bills.
roof insulation is no-contest. The floor wins every time. Insulating the floor is standard practice for an unfinished attic space. The exception to this rule takes place when families opt to convert an unfinished attic space into something usable or livable.
Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.
The right amount of insulation, combined with a well-sealed home, can save you an average of 15% on your annual heating and cooling costs. Heat rises and, without proper attic insulation, the heat you pay for will warm your roof, not the inside of your house.
The Environmental Protection Agency (EPA) estimates that homeowners can save an average of 15% on heating and cooling costs by sealing air leaks and adding attic insulation. This helps keep your house from losing heat in the winter and helps you stay cooler in the summer.
Wall and Floor Temperatures
Here's another great way to tell if your home is well insulated. Use your hand to check the temperature of interior walls, floors, and ceilings. If they feel warm and dry, you are in good shape. If they feel cold or damp, then you have an insulation problem.
There comes a point where too much insulation starts to have a negative effect — financially, environmentally, and in terms of the longevity of your home. So yes, it is possible to over-insulate your house. Fortunately, insulation fixation is a monkey not many people have on their backs.
In an unfinished attic, the goal of insulation is to keep the rooms below cool in summer and warm in winter. That means insulating the attic floor only—not the walls—and having vents in the roof. With a finished attic, insulation must help keep the attic areas comfortable.
A flat roof should preferably be insulated from above. A layer of rigid insulation board can be added either on top of the roof's weatherproof layer or directly on top of the timber roof surface, with a new weatherproof layer on top of the insulation. This is best done when the roof covering needs replacing anyway.
Attic insulation is installed in the ceiling plane, while roof insulation is installed on the roof slope itself, above and below the rafters.
In most cases, interior walls are not insulated during construction. Unlike exterior walls, which must meet local and state codes for insulation, interior wall insulation is rarely required. This is because interior insulation has much less impact on your home's energy efficiency – but it can still play a role.
However, installing too much insulation can backfire. Excess insulation in the attic can make a house too tightly sealed and block vents.
In many cases you can add new insulation on top of old insulation, unless the old insulation is wet, mouldy, or vermiculite. If the old insulation is dry but appears to have previously been wet, you should look for the cause and repair the problem.
Too much of anything is bad, including too much insulation in an attic. Over insulating your house and tightly sealing it too much creates a vapor barrier and forces moisture to settle on fixtures inside your home (hello, water damage!).
Another sign your attic insulation is contributing to heating issues in your home is if you notice different temperature zones throughout the house. If your downstairs living room is a comfortably warm temperature while your upstairs master bedroom is freezing, there's a good chance your attic insulation is lacking.
Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. Assumes R-3/inch. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.
Moisture accumulation: If attic insulation is not installed correctly, moisture can become trapped in the insulation. This can lead to mold and mildew growth which can cause health problems and decrease the insulation's effectiveness.
In the end, attic insulation not only helps to keep you warm in the winter; it also helps to keep the whole home cooler in the hot and sticky summer months.
It can reduce your energy bills – more than 50% of a home's heat is lost through roofs, walls, and other air leakage points, causing your heating system to overcompensate and thus costing you more money. It's flexible enough to insulate areas that'd be more difficult or impossible to otherwise.