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, say 68° F, all year. Over time, building standards have increased the required minimal insulation in attics for new construction. These standards vary based upon your home’s 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 PA. 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 approximate thickness (depth) and approximate R-value should be reported. Obviously, the insulation within fixed wall and ceiling coverings will rarely, if ever, be visible to the inspector.

In many homes’ attics, there are insulation voids or uneven areas and, sometimes, even places where attic insulation is missing. Each of these can lead to energy inefficiency (meaning high heating and cooling bills) and an uncomfortable home. The below IR/digital photo overlay image shows cold attic air contacting this master bedroom’s ceiling in many places due to improperly installed and missing attic insulation. Luckily, addressing this issue is relatively simple.

Before you start…

Before you add attic insulation, however, something very important to do first is air seal areas where pipes, wires, ducts, etc. penetrate from living space up into the attic. These penetrations are most often at the top wall plates. The reason why air sealing is so important is because these small openings allow heat and moisture from moisture up into the attic. Expandable foam can be used to properly air seal these pipes, wires, and ducts pass through the framing. A good builder will do this air sealing before installing drywall and insulation but most homes (especially those built before approx. 2005 or so) lack this extra detail. If enough heat is able to enter the attic at these unsealed pipe and wire openings, adding more insulation may be less beneficial. This heat can also lead to ice dams as it can melt snow on the roof which will refreeze at the eaves where attic heat no longer reaches.

Air sealing has been accomplished in this attic where plumbing and wiring penetrate framing into the attic space. Photo courtesy of Advanced Home Energy.

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. Fiberglass batt insulation is still used in vertical exterior walls since blown-in (loose fill) insulation won’t easily stay in place in these areas when building the wall. Netted blown-in insulation is an option, however not very common, in exterior walls insulated from the interior. A netting material is installed and then the blown-in insulation is installed between the netting and the exterior wall sheathing.

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 to and also must be in contact with the wall or ceiling covering for the intended R-value.

Rolled fiberglass batt insulation

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. Over time, blown-in insulation (both blown-in fiberglass and cellulose) will settle a little over time after installation as small air pockets, etc. will naturally go away; this insulation settlement doesn’t lower the R-value, however.

Blown-In Fiberglass Insulation

Blown-in fiberglass is similar to rolled fiberglass batts except it is not itchy like the older fiberglass batt insulation and instead of it being in rolled batts, this material is loose and gets blown in. Blown-in fiberglass generally comes in white, yellow, or pink colors depending upon the manufacturer. The R-value of blown-in fiberglass is about 2.75 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 and wasted heating and cooling in the home. 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 a push-up panel (aka ‘a skuttle’) in room or closet ceilings and doors with walk-up steps are common in most older homes. 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 attic access location should be fully insulated. Modern standards also require weather-stripping of the access panel, as well, 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. If your attic access consists of a pulldown ladder, there are also special insulation kits specifically designed for them.

For example, take an attic that is 30′ x 20′ (600 sq ft) in size with an attic access panel of 3′ x 2′ (6 sq ft).  The attic is fully insulation to R-49 but the attic access panel lacks any insulation (making it effective R-0). Doing a quick insulation derating calculation, this would lower the overall effective attic R-value to 22, not 49. Imagine paying for R-49 insulation but only actually getting less than half that R-value because the attic access panel lacks insulation.

The above visual/infrared photo overlay shows a bedroom closet ceiling access panel which is uninsulated. The attic heat (indicated in yellow) is finding its way into living space at this location in the summer. A similar but opposite thing will happen in the winter. In cold months, the area shown in yellow here would be dark blue due to cold attic air contacting this access panel and heat from living space would be lost to the attic.

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 perpendicularly 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 a home inspection, verifying whether there is insulation (and how much, if any) under the attic flooring can be difficult or impossible. 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.

Also, if there is any heating/cooling ductwork in the attic, it should be properly sealed at its seams and be properly insulated. Most HVAC ductwork in modern attics is insulated however this flex-duct insulation has a relatively low R-value. Adding additional thermal insulation over the ductwork is recommended.

If there are bulkheads or uninsulated areas (walls or ceilings) above a staircase, make sure these also get properly insulated. I’ve inspected many homes over the years where there were exposed (uninsulated walls or ceilings) above a staircase that was only observed by walking the attic. This leads to energy inefficiency in the home and cold or hot rooms.

Attic Ventilation – Often Overlooked

An important issue to mention is that most 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 under the roof. 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. Not doing so is a common cause of attic mold and increased heating/cooling bills. 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.

Recessed can lights in ceilings also present an additional issue. Some can lights are IC-rated meaning insulation can be installed directly to the can light assembly. Others are non-IC-rated meaning that a gap needs to exist between insulation and the light in order to prevent a possible fire due to the heat generated by the light fixture. These gaps, however, lack insulation and are a common point of lost or gained heat between living space and the attic. Ideally, recessed can lights are not recommended due to their energy efficiency loss (the ceiling, in essence, becomes a piece of ‘swiss cheese’ in terms of energy efficiency), but if they must be used, install only IC-rated recessed lights. Also, power vent fans (either roof or gable mounted) should NOT be used for multiple reasons including wasted energy and roof shingle warranty issues. Proper attic ventilation and attic insulation work together; read my Attic Ventilation article for more info on that topic.

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 fall into the space above the baffle and block the soffit in-take air.

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 to the home’s outer walls. 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 (resulting in higher heating and cooling costs), and/or premature roof deterioration.

One type of potentially dangerous insulation, sometimes found in homes built in the 1930s through the 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. Learn more about asbestos by visiting these websites:
https://www.zonoliteatticinsulation.com/faqs/
https://www.asbestos.com/exposure/home/
https://www.epa.gov/asbestos/protect-your-family-asbestos-contaminated-vermiculite-insulation

The below photo shows Zonolite/Vermiculite insulation.

© 2017 Matthew Steger
All Rights Reserved

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Matthew Steger is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), and an electrical engineer. He can be reached at matthew@thehomeinspectorsnotebook.com. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.