We’ve already spoken on this website about insulation requirements for your basement but what about the attic? Would you be surprised to know that a significant amount of a home’s heat loss occurs in the attic, even more than the basement in fact.
About 25% of the heat lost in a home is through the attic and potentially more if it is poorly insulated. Hot air rises and escapes through cracks and improperly vented attics.
Home builders will generally only meet the bare minimum requirements for home insulation particularly in the attic. Better insulation in the attic can lower heating costs if the current level of insulation is too low.
How insulation is installed in an attic
R value measures the insulating effectiveness and ability of a material to resist heat flow and thus heat loss. The higher the R value, the better the level of insulation. While the attic is an important part of the home to insulate, the walls in your basement and other floors in your home should be insulated too.
In the attic, loose fill insulation is normally used as it can be blown in with a pump and hose much quicker and more efficiently than manually installing fiberglass insulation batts (rolls) like in the rest of the home. It is blown on the floor of the attic so that it covers it completely until the desired R value is reached.
The perimeter of the attic floor has air vents leading out of the house (soffits) which provide air flow from outside the home up through the attic and out the air vents at the top of the roof. These vents should be left free of insulation so air flow from outside can be maintained.
By insulating the floor of the attic, it acts as a barrier and prevents rising hot air from escaping through the attic along with the cold air that is circulating through the soffits.
Heat loss through the attic
Even with proper insulation, the attic still loses heat. The attic of a home is a major source of heat loss in homes for several reasons:
- Hot air rises so naturally hot air eventually makes it way to the highest point of the house which is the attic.
- Improperly insulated attics allow hot air to flow through the ceiling, cracks, gaps, etc and up exiting the house through the roof vents.
- The roof of most homes is made with a wood frame which has a very low R value meaning it is capable of losing a great deal of heat which is why attics are insulated.
- Roof vents may be installed improperly which further allows heat to escape.
- Cracks, holes and gaps in the attic and roof itself also allow hot air to escape.
Recognizing heat loss through the attic
If you live in an area that receives heavy snow fall throughout the winter, you can spot potential heat loss areas on your roof:
- Patches of melted snow on the roof where you can see the roofing tiles but the rest of the roof is covered with snow is a sign of heat loss.
- Icicles hanging down from the eaves is another sign of possible heat loss.
When you look at the roof and it’s covered with a small layer of snow but you notice some areas that are completely clear of snow, it’s likely heat is leaking through the attic and roof. That’s why the snow has melted in those areas. Icicles are another potential sign.
If you notice your heating bills in winter are higher than they should be, have increased over time or are higher than your neighbors, consider speaking with a roofing or insulation pro to test your attic and roof for heat loss.
The balance between hot and cold air in the attic
The attic is the place in your home that requires a careful balance between heat and cold:
- In a hot summer, your attic can get very hot which makes the top floor of your home difficult to cool and can also prematurely age and wear your roof shingles. In this instance you want air flow and the ability for heat to escape through the vents to cool the attic.
- During a cold winter, you want to retain as much heat as possible and avoid heat loss through the attic so that you don’t spend more money on heating.
- In winter, your attic should be slightly warmer than the outside temperature as you’d expect that some heat will always leak into the attic to keep it even slightly warmer.
- In summer, your attic shouldn’t be more than 10° – 20° degrees higher than the outside temperature.
R value insulation levels for the attic in a home
Older houses tend to have less insulation that is often outdated and moldy which is bad for heat retention and a health hazard. Loose attic insulation should be fluffy to maximize R value but when it gets damp, moldy and compressed, it loses its insulating power.
Many older homes can probably benefit the most from new modern insulation also due to house design which isn’t as energy efficient as modern houses.
If you live in a cold weather environment that experiences very chilly, snowy, icy winters and you use an R value of 20 – 25 in your basement, your local area will normally prescribe an attic R value of 38 – 60 to properly insulate it and avoid massive heat loss.
The importance of insulation to your home energy spending
Over time, we have seen an interesting change in the way US households spend money on energy. Here are some comparisons regarding the percentage of total energy
costs in US households spent on heating and air conditioning (AC):
1993: 58% of total residential energy use was spent on heating and AC.
2011: 48% of total residential energy use was spent on heating and AC.
2015: 39.1% of total residential energy use was spent on heating and AC.
While total energy consumption in the home has gone up due to the proliferation of bigger homes and more modems, PCs, tablets, cellphones, video games and appliances, the share of residential energy use of heating and cooling has decreased. We have more energy efficient equipment and furnaces, better insulation throughout the home and better insulated windows among other things.
During the next 25 years, U.S. Energy Information Administration predicts that US homes and commercial businesses will decrease their energy usage by 0.4% every year due to increased efficiencies. The better insulated your home, the less you will spend on heating and cooling.
Can you put too much insulation in attic?
In theory, yes. First off at some point you will likely spend more to insulate than the advantage you receive from the extra insulation. Also, the attic does require airflow and the ability for hot air to rise through the vents at the top of the roof and through the soffits. The soffits are the underside of the eaves that allow air to pass through and to reduce moisture in the attic.
When insulation is either blown or otherwise put into the attic and the soffits are covered, it restricts airflow and increases the chance that moisture will develop and the insulation will become moldy. This is especially true if you have a leak in the roof through the shingles or whatever is covering the roof structure.
While insulating your attic can be a DIY project, your best best is to hire a professional to do it who offers professionalism, has knowledge of the building code in your local area and who offers a warranty.
To give you an idea of what R value of insulation is required in each geographic area, check out this website for the United States. You can also access a database to search Canada by province and city.
Is the basement where I lose most of the heat in my house?
No, not even close. How much heat is lost through the attic? A widely quoted stat is that up to 25% of a home’s heat loss is from the attic. About 15% of heat loss is in the basement. Hot air rises and air vents in the roof and soffits are required to allow proper air flow in the attic but it also leads to heat loss. The wooden structure of most roofs also allows heat loss since the R value of wood on its own is very low and thus bad for heat retention.
The attic is typically the part of the house that requires the highest R value since it’s an extremity, located at the very top of the house and a place that is not heated. The US Department of Energy suggests that proper attic insulation may reduce heating costs anywhere from 10% – 50% depending on how well insulated it is now.
Summary
While insulation installation may be seen as a DIY project you can do on the weekend, it’s something best left to the pros. The amount of insulation is important but the quality of installation is even more so, to properly cover and address gaps and air leaks to ensure consistent temperatures throughout your home year around.
To further address insulation, energy costs and overall utility costs in the home, consider upgrading old energy inefficient windows, upgrading insulation levels and look at the option of a heat pump and tankless water heater.
But as mentioned above, when you can potentially reduce energy costs by 10% – 50% by better insulating your attic, it’s most likely the single easiest and most effective way to do so.
