How to Inspect an Attic to Ensure the Insulation is Effective
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How to Inspect an Attic to Ensure the Insulation is Effective

This article was written as a response to the question: How do I inspect my attic insulation to ensure its working effectively

Examining an attic may be a little disconcerting as a wide variety of materials have been used as insulation, in the past. Old houses, generally over 100 years old, were insulated with many different types of natural materials ranging from horse hair, goose feathers, wood chips, sawdust and newspaper, if found insulated at all. From around the turn of the century to the 1960 or 70s, mineral based insulations such rock wool, asbestos and vermiculite had become increasingly more popular. With newer homes, since the 60’s, fiberglass, cellulose and foam type products are the most common insulation products used for energy savings and reduction of heat loss. Ventilation is an important co-component in buildings as the two often significantly have a direct impact on the effectiveness of the other. Ventilation of an attic space would require a separate Factoid in itself, or more, to fully explain, clarify and understand. Open, accessible attics are easy to improve while vaulted, cathedral, finished attic spaces with no areas or space for activity, would usually require a major undertaking.

It’s a good idea to establish what the type of insulation the substance is, that you are evaluating, first. While age may be a primary consideration, some old timers may have been convinced that a certain material worked best and that obsolete material may be found in some newer homes. Older, natural based insulation is, more often than not, a fire safety hazard, such as goose feathers in contact with older knob and tube electric wiring, and when found, replacement should be immediately considered.

Mineral based insulation, such as asbestos, have been around for centuries but started to gain an increase in popularity as building insulation around the early 1900’s. Asbestos, rock wool and vermiculite was used due to the good insulating characteristics, durability and fire resistance. Asbestos generally is a powdered or thread like, stranded material that is usually gray to white but may be brown or blue. Rock wool is often very similar visually and professional testing is best to determine the difference between the two types of insulation. Vermiculite is a mineral based insulation that was mined in the US and some has been confirmed by the EPA as asbestos contaminated. Uncontaminated vermiculite today is used in some potting soils for gardening. The material looks like small, ¼ X ¼ X ¼ inch sections of mica, for the amateur geologists, or a silver costume jewelry, for others, as a simple means of identification. While rock wool was poured or in batt form (see fiberglass for batt description), asbestos and vermiculite were usually bagged and poured into the spaces between ceiling joists in the attic. As asbestos and asbestos contaminated products were occasionally used, any substance that cannot be positively confirmed should be viewed as suspicious, and professionally evaluated or tested. Under no circumstance should any substance or material be disturbed at all, when suspicious. Also, be sure to look under the top layers of insulation as many attics have been insulated with two or more different types of insulation with older insulation below the top, newer layers. Many times bags of insulation product, either emptied or still full, are found to have been left behind and the printed information on the bags will give you a good indication as to what material was used.

A quick stroll through any building supply dealer would give you an idea as to what modern insulation products look like such as fiberglass, cellulose and foam type insulations. Fiberglass is generally pink, white or yellow, a stranded, thread like material, a mat of threads in a batts form or a loose material that is generally blown in place. Fiberglass batts are of different width, depth and length either in rolls or folded sections precut to specific lengths. Cellulose is a gray material that looks like the materials it is, ground up newspapers dyed gray. While fiberglass is naturally fire resistant, cellulose has been treated for fire resistance. Foam board resembles either a loosely packed or tightly packed Styrofoam. Foam board insulations are occasionally used in horizontal attic insulation applications but is expensive and normally used for specific purposes only as it burns readily and should be covered. More recently, a fire resistant spray type foam insulation has become increasingly popular, the material sprayed between roof structure in the attic spaces, however this evaluation would require more professional equipment and expertise. For greener installations, soy based spray type foam insulation has become recently available.

After the material has been established, the depth of the insulation should be determined. Traveling through an attic space is a balancing act. If no flooring exists to walk on, crossing through an attic space requires one to stand on the ceiling joists, the horizontal wood framing installed upright in the attic floor. With truss construction, premade roof structure composed of triangles usually with metal plates at various intersections, travel requires standing on the bottom cord. The bottom cord is the lower most horizontal wood section of the truss assembly. The floor joist or truss sections are 1 ½ inches thick and 16 to 24 inches apart. Placing weight on the ceiling area between a truss or ceiling joist often means falling through the ceiling, a most unpleasant feat that usually evokes a rather unhappy response from one’s partner, especially if standing directly below when this event occurs.

Rather than an explanation as the R value, the insulation value at certain depths, this information will pertain to measuring depth or thickness of the insulation. As a general rule of thumb, 12 inches is a good insulation depth of fiberglass or cellulose, in most sections areas of the US. With colder areas, the more the better, up to 24 inches of depth will provide additional energy savings. Fiberglass insulation tends to expand after placement and cellulose tends to settle after installation. Allow room for fiberglass to expand and overspray cellulose by a few inches allows adequate insulation levels. Both fiberglass and cellulose should not be compressed. The placement of loose plywood as flooring, storage of personal belongings or any other type of material directly on insulation decreases the insulation properties, and often dramatically. If flooring is needed for storage, framing lumber (2X4, 2X6, 2X8, etc) should be placed perpendicular and the storage flooring placed on that frame. This should hold the flooring and storage above the insulation and will allow the insulation free area to expand as needed.

Any gaps, open areas, un-insulated areas should be filled with insulation. Hatches, whole house fans, pull down stairways, should be fitted with insulation jackets, sections that can be removed and replaced, as needed for access. Insulation jackets are becoming available preformed for the mentioned openings or a custom made jacket can be made from wood, foam board and/or fiberglass batts.

Many older recessed lights were not constructed to be in contact with insulation. A cage or dome type frame can be constructed of chicken wire or garden fence and insulation placed on the cage to prevent contact with the light enclosure but allow adequate insulation properties. Left un-insulated, recessed lights produce condensation when the bulb heats the surrounding enclosure, dripping into the house, causing alarm. Many roof replacements have been performed that could be attributed to un-insulated recessed light condensation. Any furnace ducting, even insulated ducting, should be covered with additional insulation for increased energy savings. Be careful around metal chimneys, as insulation should not be in contact with the metal itself. At least 2 inches of space should be maintained from most metal chimneys. Fire resistant insulation may be placed in direct contact with modern masonry chimneys. Seal any openings adjacent to plumbing vent pipes or where electrical wires pass through from below into the attic, as these openings are similar to small chimneys, allowing warm, heated air to rise into the attic. Use caulking or stuff small sections of insulation at these openings to act as a sealant.

On very cold days look in the attic for ice forming at nails or on the roof sheathing, this being another indication of inadequate insulation and poor ventilation. After ice forms in an attic space and begins to melt, this is often regarded as roof leakage, another unnecessary roof replacement. Just opening the attic hatch allows warm air to flow into the space and swiftly melt the ice that had formed in the attic creating a raining effect. Look for water staining through the attic space where the water drops had fallen previously. The cycle of frost and melt repeats often throughout cold weather due to temperature changes.

If winter, look at the roof after snowfall if followed by a period of relatively calm weather. If no snow drifting has occurred, the snow melt should be relatively consistent on the roof. Anyplace on the roof where the snow has melted, or has become depressed in relation to adjacent areas, should prompt attention to check when again at the interior.

The presence of large, long icicles and ice dams in most instances indicate a lack of adequate insulation and often improper ventilation. As snow melts on a roof from heat loss within the structure, the water flows to the lower perimeters and re-freezes at the roof overhang to create ice dams. Snow melt from sunshine tends to evaporate quickly and while sun melt may create some icicles, it is generally not as pervasive. As a snow melt/ heat loss cycle repeats, the ice dams become quite large and water may back up under the roofing material and flow into the house. Again, proper ventilation plays a significant role in eliminating ice dams and icicles, so adequate ventilation should also be taken into account.

The time it takes to recover the installation and material costs can range from1 to 5 years with many different factors taken into consideration. Insulation is just one of the many components in a system that may have a significant impact on other components. Other than the obvious, adequate insulation may help extend the service life of a roof, prevent freezing or additional stress of some other building components, and prevent heating and cooling systems from cycling often. With the ease and relatively low cost that attic insulation provides, every responsible owner should insure an attic is adequately insulated

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Comments (1)

Good morning Peter, This is an excellent article and, since you brought up old Knob and tube wiring I would like to add a comment or two. The first comment is for readers who may not be familiar with this wiring method. Knob and tube wiring was common in homes built up until the 1940s and in some areas well into the 1950s. Knob and tube wiring was a wiring system where the concealed conductors were supported on porcelain or ceramic standoffs and ran through porcelain or ceramic tubes where the single conductors passed through framing members. Comment two. According to the latest revision of the NEC (National Electric Code), NFPA (National Fire Protection Association) Publication 70, Knob and Tube wiring is still a viable wiring system but new knob and tube wiring may only be installed to extend an already existing knob and tube wiring system or used by special permission (NEC 394.10(1)(2)). Under no circumstances can any hollow space containing knob and tube wiring be insulated with any type of insulating material. To insulate such a space is not only a fire hazzard, it is a direct violation of the NEC (NEC Setction 394.12(5)) and it violates local building codes as well. Local building codes can have more stringent requirements then the NEC but they have to at least meet the minimal safety standards set by the NEC for electrical installations. Comment three. Although knob and tube wiring systems are still allowed, it is best to replace such systems with more modern systems, such as AC (Armored Cable or NMC (Non-metalic Clad Cable) whenever possible. The newer systems allow you to insulate the walls, ceilings, and floors of your home and the money you save in heating and cooling your home will help defray the cost of the electrical upgrade. Besides that, homes with knob and tube wiring had a service ampacity of 60-Amperes which is totally inadequate for today's electrical loads.