Insulating a Hollin Hills House

The insulation installed originally in Hollin Hills houses is virtually non existent. Usually it consists only of a few layers of paper and a sheet of foil, which was supposed to act as a radiant and vapor barrier. It’s insulating value is marginal. Upgrading insulation is clearly called for, but often is difficult.

Insulation of ceilings in Hollin Hills falls into two categories based on the model of the house. Houses with an attic crawl space are easily insulted with a blown in type product, usually either fiberglass or cellulose. Achieving an R-value (measure of resistance to heat flow, single pane windows have an R value of one) of 30-40 is usually attainable. It is important to make sure that the soffit vents, which allow airflow into the attic, are not blocked by the additional insulation. As this requires a level of attention to detail not normally exercised by installers, careful supervision is necessary.  In houses that have large gable vents, ridge vents, or other methods of attic venting, maintaining the soffit vents is less important.

Maintaining proper roof ventilation is important for two reasons. In the summer the venting allows for the escape of hot air that builds in the attic due to solar heating of the roof. Attic temperatures in the summer can reach in excess of  120 degrees. As heat radiates equally in all directions, much of this heat is transferred into the living space below, causing the air conditioning to work harder. Installing a temperature activated exhaust fan in the attic is probably the most cost effective way to help cool the attic and reduce AC costs.

In the winter, the venting allows for the escape of moisture laden air from the attic. Activities in the house, such as showering, cooking, and breathing, all release moisture into the air, some of which finds its way into the attic through wall and ceiling penetrations, such as light fixtures, and electrical outlets and switches. If there is no way for this moist air to escape the attic , the moisture will condense when it hits a cold surface, such as the underside of the roof. This creates a moisture problem in the attic, which can lead to mold growth, and eventually, to rot. Properly vented attics in Hollin Hills generally do not have this problem.

An additional common source of attic moisture is improperly vented appliances. Often the bathroom exhaust fan, dryer, or kitchen hood fan blow into the attic, rather than being vented to the exterior. This situation is very detrimental to the house and should be corrected.

An additional concern when adding attic insulation is to make sure that recessed ceiling lights are rated for contact with insulation. Recessed lights generate heat, and if the housing is not properly designed for contact with insulation, the fixture can over heat. A quality fixture has a thermal  switch which turns the fixture off when it overheats. Lights that cycle on and off by themselves are a sigh of lights that are getting too hot. An over heated fixture without the thermal switch risks starting a fire. Most original and older recessed lights are not designed to have insulation placed around them, nor are they air tight. These old housings allow conditioned air from the house to escape into the attic. This both exacerbates the moisture transfer issue, and wastes energy. The solution to over heating is to either install some type of baffle to hold insulation 3” away from the fixture, or to replace the fixture with an insulation compatible, air sealed housing. An immediate short term fix is to swap incandescent bulbs for more efficient and cooler running fluorescent bulbs.

Insulation also must be kept away from furnace and water heater flues.

The Hollin Hills houses that do not have attics are far harder to insulate. However, the newer versions of these houses usually have some fiberglass insulation in the ceilings. Basically, one has two options for adding ceiling insulation. The first is again to install a blown-in product. Since the space to insulate is divided up by the roof rafters and other framing, each space has to be drilled to have the insulation blown into the cavity. This means lots and lots of 2” diameter holes in the ceiling. All these holes then need to be patched, and the ceiling then painted.

As with the attic, one must be careful not to insulate around light fixtures and flues.  Some loose blown-in products may trap moisture from the living space, basically acting as big sponge, and as the insulation becomes damp it looses its insulation value.  The roof ventilation in flat roof and cathedral ceiling houses in Hollin Hills generally is inadequate. Most of these houses have ineffective ventilation, leading to moisture build up in the ceiling cavity. This moisture accumulation leads to the degradation of the roof plywood, and occasionally, damage to the framing. Many of these houses actually have the roof plywood rotting from the inside, even though the roof itself is intact and not leaking. The roof over the central core of the house where the bathrooms are located is particularly susceptible to rot from poor venting. Severe structural damage has occurred in Hollin Hills houses due to a combination of excessive indoor humidity and lack of proper venting. Due to the potential problems that can be caused by moisture in the ceiling cavity, if one is contemplating blown in insulation, efforts must be made to eliminate the possible entrance of air from the house into the ceiling. This means sealing around all light fixtures, fans, chases, flues, and other ceiling penetrations. Use of kitchen and bath fans is a must. Dryers vents must be carefully sealed and vented to the exterior. As air that enters wall cavities through switch and outlets can reach the ceiling cavity through holes drilled in the framing for the wiring and plumbing, sealing switches and outlets may also be necessary.

An alternative to loose blown is a product called dense pack cellulose. This product is also blown in, but as its name implies, it is densely packed during installation. Dense pack cellulose insulation manufactures claim that by limiting air migration through the insulation, dense pack insulation is suitable for unvented applications, such as flat roofs and cathedral ceilings. It also has a higher R-value than fiberglass.

When re-roofing, it is not unusual for much or all of the roof plywood to need to be replaced. This scenario, with the roof deck removed, is a perfect opportunity to insulate the roof, either with fiberglass batt or loose fill insulation. However, as the roofer is more concerned with getting the roof back on before it rains than he is with insulation, one must have a plan ready in advance. Again, one must be careful not insulate around non-insulation rated light fixtures and flues.

A better, although more expensive solution, is to insulate with a sprayed foam product. The foam creates a 100% air seal, as well as a vapor barrier, so the entire venting issue can be ignored. The foam has a higher R-value than fiberglass, and also eliminates all air leaks through the ceiling. The problem is, to my knowledge, a foam product does not yet exist that can to be blown into a closed cavity. So to use a spray foam, the entire ceiling needs to be removed. The foam is sprayed in, either by itself, or with another insulation product over it, then the ceiling needs to be reinstalled. Obviously this is an expensive and inconvenient process. Removal of the ceiling also facilitates replacement of outdated wiring and electrical fixtures. Spray foam could also be installed from above when the roof is off. Spray foam is well suited to new construction, and should be used wherever possible to maximize R-value and minimize air infiltration.

Since the impermeable spray foam prevents the moisture from ever reaching the cold plywood surface, this method of insulation is ideal for the flat roof and cathedral ceiling houses.

Questions and comments are welcome at 703-718-0804 or email us for more information.