Matthew Steger WIN Elizabethtown

Attic Insulation

One of the simplest ways to lower your home's heating and cooling costs is to properly insulate your attic. Attic insulation works by creating a thermal blanket between conditioned (living space) and unconditioned (your attic) space. Think of a cold winter night. You put an extra blanket on your bed to help retain your body's heat. Additional attic insulation follows the same idea. Attic temperatures can easily range between 130°+ degrees F (summer) to less than 10° F (winter). Since heat is always trying to move from warmer areas to cooler areas, properly insulating your attic can help keep your home closer to the desired temperature all year. Over time, building standards have increased the required minimal insulation in attics for new construction. These standards vary based upon location; northern climates generally require more attic insulation than southern climates due to our longer heating season.

Eighty years ago, attic insulation was often overlooked since energy was cheap by today's standards. In the 1970s when energy prices started to go up, many areas required R-24 minimum for attics. By the late 1990s, R-30 was the norm. By 2006, R-38 was standard for attics in most northern states. As of Oct. 2018, R-49 is now standard for attics in new homes in most northern states. These R-values are the minimum required by our modern building standards. “R-value” is a material's thermal resistivity to allowing heat passage through it. The higher the R-value, the more difficult it is for heat to pass through; this means that insulation helps slow down heat movement from one area to another. Since a material's R-value is "per inch" based, the thicker the insulation, the higher the R-value.

As part of a home inspection, the home inspector should inspect and report on the visually accessible installed insulation, such as in attics. The approx. thickness (depth) and approx. R-value should be reported. Obviously, the insulation within fixed wall and ceiling coverings will rarely ever be visible to the inspector.

attic insulation rolled-fiberglass

Rolled fiberglass insulation

For decades, rolled fiberglass batt insulation was the most common insulation type. It worked but required considerably more labor to install (compared to the blown-in types) since it required each piece to be carefully rolled into each framing bay between ceiling rafters or trusses. Rolled fiberglass has a typical R-value of about 3.0 per inch. So, if installed in new construction, you would need about 16" to meet R-49. Even in new homes, if there are vertical walls that separate living space and unconditioned attic space, fiberglass batts are still used in these areas as blown-in insulation often won’t stay in place vertically. Exterior walls within living space also have fiberglass batt insulation installed in most cases.

No matter the type, insulation should not be compressed, such as placing stored items on the insulation or packing the insulation too tightly. Doing either lowers the R-value and, therefore, the insulation's efficiency. Insulation should be allowed to be as loose as it wants in order for it to settle naturally over time. The insulation should make contact with the interior wall covering.

Blown-in or Loose Fill Insulation

Blown-in (also called loose-fill) insulation is found in most modern attics and is usually either blown-in fiberglass or cellulose. The method of installing these types of insulation consists of 2 parts: an outside hopper in which the packaged insulation is shredded and the hose on the attic side which is used to spray the loose insulation into place. This is a 2 person job, however insulating an average sized attic with blown-in insulation can often be done in less than 30 minutes. Insulating an average attic with rolled fiberglass batts can take more than half a day

attic insulation blown-in-fiberglass

Blown-in fiberglass insulation

Blown-in fiberglass is similar to rolled fiberglass batts except it is not itchy like the older fiberglass and instead of it being in rolled batts, this material is loose and gets blown in. This product does compact a little naturally over time, which removes air pockets helping its efficiency. Blown-in fiberglass generally comes in white, yellow, or pink colors depending upon the manufacturer. The R-value of blown-in fiberglass is about 2.5 per inch. Since it has a lower R-value per inch, it takes more blown-in fiberglass insulation to reach a desired total R-value compared to fiberglass batt or cellulose. It takes about 20” of blown-in fiberglass to reach R-49.

Blown-in cellulose insulation

Cellulose is a shredded recycled paper product with additives such as borate to help prevent it from being flammable. The composition of cellulose is approximately 80% recycled newspaper. Cellulose is denser than fiberglass so it can also help in noise dampening. The R-value of cellulose is approximately 3.5 per inch. It takes about 14” of cellulose to reach R-49. Therefore, cellulose is a better thermal insulator compared to the same amount of fiberglass batt or blown-in fiberglass. Like blown-in fiberglass, cellulose also fills in very well around framing, ductwork, and pipes and compacts over time slightly so air pockets and missed areas are a minimum. In older homes where there is likely no wall insulation, cellulose can be installed by drilling holes in the exterior wall bays and blowing in cellulose.

Minimizing air pockets and missed areas for any type of insulation is important because convective currents (air flow) lead to inefficiency of insulation. Cellulose does weigh more than blown-in fiberglass when comparing the same R-values.

A Common Attic Flaw

Based upon inspecting thousands of homes for nearly 20 years, a common flaw (yet easily repaired) that I find in most homes is the attic access location not being properly insulated. Most attics are accessed via push-up panels (aka 'skuttles') in room or closet ceilings. For attic insulation to be efficient, all areas of the upper level ceiling (the ‘attic floor’) must be adequately insulated. If the 2'x2' attic access panel is uninsulated, even if the rest of the attic is sufficiently insulated, you know where a good part of your home's heat gain or heat loss will occur. In the case of an uninsulated attic access panel, the only thing separating 70° F living space and the 10° F (winter) or 140° F (summer) attic is a thin piece of plywood which has very little R-value. The access panel should also be properly weather-stripped to ensure a better seal when the access panel is in place. If the attic is accessed via a walk-in or walk-up with a door, the door should be an exterior insulated door and properly weather-stripped.

An attic insulated to R-49 but lacking insulation at the attic access panel, can render the overall attic insulation down to less than an R-10. Think about that for a minute… it tells the story of why insulating the attic access panel or door is so important.

The above visual/infrared photo overlay shows the corner of a bedroom ceiling that has very little insulation installed. The issue is instantly found using an IR camera. Read more about our Infrared Thermography service.

How Do I Add More?

Adding insulation to your attic is normally a fairly simple process and can pay for itself in short order. If you are installing new fiberglass batt insulation over older fiberglass batts, the new batts should be installed perpendicular to the direction of the older batts. Blown-in cellulose or blown-in fiberglass can be added right over older batts or other blown-in insulation.

Some utilities offer rebates for energy upgrades such as adding more insulation so be sure to contact your electric and natural gas utilities to see what rebates they may offer.

When I perform infrared thermography (aka thermal imaging) during my home inspections, I often find uninsulated attic access panels before I even enter the attic. As noted above, the attic access panel or door should be insulated to the same R-value as the rest of the attic. To help reach the R-49 value, one or more pieces of rigid foam board insulation are often attached to the top of the access panel and then the remaining insulation value is obtained with a piece of fiberglass batt.

In older homes that have a walk-up attic, some insulation may already exist below the fixed floor boards; since we don't remove flooring as part of an inspection, verifying whether there is insulation under the flooring can be difficult. In most cases, if there is any insulation below the flooring, it is likely minimal. Additional insulation can be added on top of the attic flooring. Keep in mind, however, if the home has active knob and tube (K&T) wiring (often found in homes built prior to 1950), there should be no thermal insulation installed near that type of wiring as it can overheat and present a fire hazard.

Attic Ventilation - Often Overlooked

An important issue to mention is that attics must be proper ventilated. In most modern homes, soffit and ridge venting are used for balanced passive air flow. Adequate attic ventilation helps prevent winter ice dams, attic mold, and helps prolong a roof covering's life by preventing excessive heat and moisture accumulation. Besides simply insulating an attic, openings into the attic, even small ones where ductwork, wiring, or plumbing passes through framing should be properly sealed, such as a proper expandable foam product. Often overlooked by home owners and contractors, these small openings can allow large amounts of heat and moisture from the home to enter the attic. Power vent fans (either roof or gable mounted) should NOT be used for multiple reasons including wasted energy and roof shingle warranty issues. Read my Attic Ventilation article.

insulation soffit-vent-baffle

The baffle (this one is pink) helps prevent
the attic insulation from blocking the soffit vent.

If the home has soffit venting installed, baffles should be installed at the soffits (eaves) to prevent the attic insulation from blocking the needed intake air at the soffits. Ensure that the insulation level does not reach the height of the baffles, otherwise, the insulation will overflow and block the baffles.

Baffles are pieces of cardboard or rigid foam that get installed against the roof sheathing between the trusses or rafters to create an open channel to allow cool air entering the soffit venting to rise towards the ridge venting creating an even air flow at the roof's underside. The baffle in the above photo is rigid foam. The baffles still allow the attic insulation to extend towards the roof's lower edges. Should intake air be blocked at the soffit venting, the attic ventilation will be compromised. This can result in attic mold, deteriorated roof sheathing or framing, excessive heat in the home and attic, and/or premature roof deterioration.

One type of potentially dangerous insulation, sometimes found in homes built in the 1930s through 1950s, is Vermiculite insulation. This type of insulation looks like small pellets and likely contains asbestos. Asbestos is the third leading cause of lung cancer after smoking and radon. Vermiculite should not be disturbed (touched, walked on, etc.) in any way and, ideally, should be removed by a qualified asbestos contractor. Asbestos also needs to be properly disposed of in an approved manner. The below photo shows Zonolite/Vermiculite insulation. Learn more here: https://www.zonoliteatticinsulation.com/faqs/ or https://www.epa.gov/asbestos/protect-your-family-asbestos-contaminated-vermiculite-insulation

In summary, properly insulating your attic can more than pay for itself in lower heating and cooling costs plus it will make your home more comfortable for years. From my experience, most homes (even many only 20 years old) would greatly benefit by having additional attic insulation installed.

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My full list of technical and home maintenance articles can be found here.

© 2016 Matthew Steger

Matthew Steger, owner/inspector of WIN Home Inspection, is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), and an electrical engineer. He can be reached at: 717-361-9467 or msteger@wini.com.

WIN Home Inspection has provided a wide array of home inspection services in the Lancaster, PA area since 2002. This article was authored by Matthew Steger, ACI - owner of WIN Home Inspection in Lancaster, PA. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.