If you add insulation to your attic, add ventilation too.
Here is why it’s really important that you ventilate your attic as well as you insulate it.
There is no doubt that every home needs attic insulation. It is the single best way to reduce your energy costs and to make your home more comfortable in winter, and in summer.
Without insulation, 70 per cent of your heat will escape through your attic. Compare that to 21 percent through doors and windows and 9 percent through the outside walls. Consider too that hot air rises and will naturally go up and out.
Now, trapping that hot air in your home is a good thing but overhead you will have a relative airless environment between the insulation and the actual roof and this is not so good. Without adequate ventilation, condensation will form where the warm air meets the colder surfaces and this will encourage mildew and mold, deterioration of the wood framing and infestation.
It’s amazing how many houses, particularly older ones, will have good attic insulation but no ventilation. So take a good look at your home and see if you have any of these four types of roof ventilation:
- Horizontal soffit vent
- Vertical gable end vent
- Upper roof “box vent”
- Continuous ridge vents at the peak of the roof
Building codes require one square foot of venting for each 150 square feet of attic floor space. As an example, if your attic is 900 square feet then you need six square feet of insulation.
Finally, you should have high vents and low vents with clear passage between them so that air flows can develop between them.