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Attic Insulation

Adam Solko, Inspector

By Chris Meis, Owner and Lead Home Inspector / Licensed Radon Professional

Having a well-insulated attic will keep your home running smoothly!

An attic is a space or room at the highest point in your home. When the highest point in your home is closed off and unfinished, it is easy to forget it is even there. That is, until you see your heating and cooling bill. By insulating your attic, you help to prevent heat loss into the attic during winter time, and reduce heat infiltration into your home during the summer.

Measuring attic insulation

How much insulation?

The amount of insulation in an attic can vary from house to house. The recommended minimum amount is R49 for new construction homes. What does that mean? R-Value is the measured resistance to heat loss for that insulation type, usually expressed in a b-the-inch value. In the case of fiberglass batting it is expressed as the total of the material thickness. An attic insulated with loose fill fiberglass to R49 will have approximately 18” of material installed at R2.7 per inch.

Problems caused by poor insulation

Poorly insulated attic spaces can lead to ice dams in regions that see snowfall. Heat loss into the attic space melts the snow on the roof from underneath. The melt runs to the edge of the roof where it refreezes into a big ridge of ice with icicles hanging down. You can usually spot these homes in the winter time, as there will be little to no snow on the roof and ice all along the eaves. Along with the heat loss in the attic are condensation issues, warm moist air from the home’s interior escapes into the attic and condenses on the materials there creating frost.


Video: An attic space with codensation frost

Fixing the problem

You might think that the answer is to add more insulation. In reality, it is not always that easy. There are certain types of insulation that should be removed first before new insulation is added. If your home is older, you could have a vermiculite insulation (such as Zonolite). If your insulation shows signs of rodent activity or bats, you might consider having your old insulation vacuumed out first to remove carcasses and feces from your attic. Sorry you had to read that – it wasn’t fun typing it, either. Follow this up by having a pest mitigation contractor pest proof your home. 

Removing old insulation presents you with a rare opportunity, you can have your contractor air seal your attic before installing the new insulation. Air escapes into the attic around light fixtures, from kitchen and bath fans, from the tops of walls, from the attic hatch, and chimney chases. Closing off the gaps prior to insulating will greatly reduce the infiltration of moisture laden warm air that was previously causing you problems.

Diagram of attic ventilation
Image depicting proper attic ventilation.

Once your attic has been air sealed, your insulator will install soffit chutes. These are cardboard or styrofoam baffles that get installed along the eaves inside the attic to prevent insulation from blocking your vents. In a properly vented attic, fresh air enters from the soffits and rises to the top of the roof and exhaust from the roof vents. This convection-driven process should remove any residual heat and moisture from the attic. After the chutes are installed, insulation is blown in using a machine that separates and distributes insulation with a blower (think cotton candy).

A warm house with a cold, well insulated and ventilated attic is the picture of health for your home. This should reduce or possibly prevent your previous ice dam issues, reduce your heating and cooling bills, and make your home more comfortable in the long term. The cost to add insulation to your attic is probably cheaper than you think. While vacuuming and air sealing do cost more, these expenses will be offset by your lower utility bills.