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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) spaces. 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, energy prices starting skyrocketing and R-24 was the norm in many northern states. By the late 1990s, R-30 was standard. After 2006, R-38 became standard in many 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.

attic insulation rolled-fiberglass

Rolled fiberglass insulation

For decades, rolled fiberglass batt insulation (seen above) was the most common insulation type. It worked well but required considerably more labor and time to install (compared to 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 13" to meet the R-38 modern standard for attics. 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 since blown-in types of insulation (discussed below) obviously wouldn't stay in place. 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.

Blown-in or Loose Fill Insulation

Blown-in or loose-fill insulation are found in most modern attics and are usually either blown-in fiberglass or blown-in cellulose. The method of installing these types of insulation consists of 2 parts: an outside hopper that the packaged insulation is placed in and 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 20 minutes. Insulating an average attic with rolled fiberglass batts may take 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 most often comes in 1 of 3 colors depending upon the manufacturer: white, yellow, or pink. 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 15" of blown-in fiberglass to reach the R-38 attic requirement.

Blown-in cellulose insulation

Cellulose is a shredded recycled paper product with additives such as borate to help prevent it from being flammable or a food source for insects. 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. 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. It takes about 11" of blown-in cellulose to reach the R-38 attic requirement.

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 since 2002, 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 and work as designed, all areas of the 'attic floor' (above the top-most level's ceiling) must be adequately insulated. This access panel or door insulation requirement is part of modern building standards; the access panel or door should be insulated to the same R-value as the rest of the attic. 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° (winter) or 140° (summer) attic is a thin piece of plywood which has very little R-value. Per modern energy standards, 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 door, the door should be an exterior insulated door and properly weather-stripped.

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 will easily pay for itself. 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.

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 a home inspection, determining if insulation exists below older attic floor boards can be difficult or impossible at times. In most cases, whatever insulation may already be there may be very minimal. In most cases, additional insulation can be added either below the floor boards or right 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. Baffles are pieces of cardboard or rigid foam that get installed against the roof 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 pink 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 Zonolite or 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. Zonolite/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/

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) can greatly benefit by having additional attic insulation installed.

© 2016 Matthew Steger


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

WIN Home Inspection provides a wide array of home inspection services in the Lancaster, PA area. 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.