Ask The Experts

Insulation & Ventilation

I am getting a huge amount of icicles hanging from my gutters this winter. I am afraid that the gutters are going to fall off. What can I do to prevent this?

The icicles are forming because heat from your home is melting the snow on your roof, which then re-freezes in the colder temperatures at the eaves. This process can create a dam of ice, causing water to back-up behind the ice and pour down through the shingles into the walls, or even into the living space. There are two basic strategies to stop the extreme icicle formation. Warming up the eaves by installing heat tape in the gutters and the lower edge of the roof is effective. But you are treating the symptoms rather than the cause. The better approach is to make your roof cooler so the snow won’t melt when outdoor temperatures are below freezing.

Adding more insulation in your attic areas will help tremendously, as will improving the ventilation in your attic. Insulation thicknesses of up to 15 inches may be cost effective and helpful. Adding well balanced ventilation may require improving openings at the lower edges of the attic, meaning at the overhangs, as well as at the top of the attic, at the ridge for example. Numerous types of screened or louvered vent openings are designed for roof overhangs and peaks.

It is also important to look for thermal bypasses. These are ways that heat from the living space can get around the insulation and escape into the attic. Some very common house components that allow heat to escape into the attic are attic access doors or hatchways, whole house fans, recessed light fixtures, chimney or plumbing chaseways that are open into the attic, and kitchen or bathroom ventilators that exhaust into the attic. Better sealing these openings and redirecting the ventilators to the exterior can be a low cost way to prevent ice-dams and excess icicles as well as save money on heating bills. You may be able to better seal or redirect these heat wasting components yourself to save even more money.

I had a new roof put on my house last summer, and now I’m getting frost in the attic. I had a ridge vent installed to prevent excess heat and moisture in the attic, but there is more frost now than before the new roof. Is the roof leaking, or is there some other problem going on?

If the frost is broadly distributed on the underside of the roof as viewed in the attic, or is greatest on the north slope, it is unlikely that your problem is due to a roof leak. Frost buildup in the attic is usually due to warm moisture laden air from the living space rising into the attic space where it condenses on the cold underside of the roof. If you are also having problems with moisture condensing on your windows, have your house checked out for excess moisture sources in the basement or the living space. This is important not only because damage to the house can occur, but because there may be health hazards associated with the excess moisture.

If you don’t have excess moisture in the house, the more likely problem is that the added ridge vent your roofer installed is aggravating the excess moisture condition in the attic. This may seem counter intuitive, but the ventilation in your attic may be unbalanced. If you have a ridge vent at the peak of your house, but no vents at the overhangs, as the air in your attic exits the ridge, the only place for replacement air to come from is the rest of the house. In other words the ridge vent is pulling heat and moisture from the living space into the attic. You may be able to solve your problem by installing vents in the overhangs or soffits along the eaves. Then as air exhausts out the peak, fresh air from the exterior will enter the attic via the eaves, rather than from your heated house. Beware of attic fans for the same reason. As they exhaust air to the exterior, they are pulling your heated air in winter, and your air conditioned air in summer, right up into your attic.

The other part of keeping moisture out of the attic is to seal up any easy paths for heat and moisture to escape into the attic from the living space, such as chimney and plumbing chaseways, attic access doors, recessed lights, and ventilators.

I am having a roof leak problem above my cathedral ceiling that seems to happen every winter. I even have water dripping out of the recessed lights, but my roofer can’t find the source. Do you have any suggestions?

There is a good chance that the water isn’t the result of leakage at all. People produce a lot of water as we live in our homes. Cooking, showering, watering our house plants, running a humidifier, etc. all put moisture in the air. Warm air carries this moisture upward through the house. If there are gaps in the interior finishes of the house, such as at electrical outlets, recessed lights, and bath ventilators, or if there are simply poorly sealed finishes, such as tongue-and-groove wood finishes or suspended ceilings, the warm air is able to carry the moisture into the walls or ceiling cavities. As the moisture moves through or around the insulation in these spaces it condenses on any cold surfaces, including the underside of your roof. The colder it is outdoors, the more frost builds up in these hidden areas, until a warm day when it all melts and comes dripping down through your recessed lights. The answer is to reduce the amount of moisture you produce, and to seal up the gaps. Older style recessed lights in particular can cause heat loss and moisture buildup. Removal, or replacement with air tight fixtures, might be a solution to your “leakage” problem.

I want to better insulate my cape style home, and am getting conflicting advice. What is the “greenest” insulation and how can I find a contractor who will use the most ecological methods?

Determining what is “greenest” is incredibly complex and may be impossible, although there are organizations that try. We would need to weigh how much energy it took to make the insulation, how much it would save when installed, how much environmental damage is caused in making the product, etc. But we can provide a quick overview. There are three broad types of insulation. Fiberglass batts are made from a natural and inexpensive common mineral. It is not considered very harmful, but can be an irritant. It is probably not the best choice in existing construction with tight quarters, such as cape style homes with eaves space floors, kneewalls, sloped ceilings, etc., because proper placement will be very difficult. Cellulose is ground up newspaper with a fire-retardant. It is a recycled material and can be blown in place, making it easier to apply, and it tends to fill the nooks and crannies of an older house well. Spray foam insulation products, usually polyurethane, are superior in terms of R-value per inch, and can be much more resistant to condensation related problems when applied in attic spaces with potentially poor ventilation, such as found in cape style homes. It is generally considered to be the best choice for a cape. However, depending on the specific type of foam, it may not be considered particularly “natural” or biodegradable, etc.

Insulating a cape style home effectively is very difficult due to inaccessible spaces and blocked ventilation. It is best done if the attic level living spaces are gutted, or in conjunction with a roof replacement. In any case, the most important step is to hire an experienced insulation professional. We recommend that you look for someone who is accredited by the Building Performance Institute. The “greenest” solution is the one that keeps you comfortable, saves energy, and contributes to the durability of your home.

I have a two year old home that was designed to be extra energy efficient. I have read that houses like mine may be too tight, causing indoor air quality issues. How can I determine if this is really a problem?

Any house built in the last decade or so may have possible air quality issues due to inadequate amounts of fresh air. In our attempt to save energy, we have reduced the amount of air that enters and exits our homes. This “tightening” of the home has generally been a beneficial process that, besides saving energy, can reduce the excessively dry conditions that plague older homes in winter, and prevent drafts or cool areas in the house. Unfortunately however, indoor pollutants can build up in a tight house. The primary gauge of poor indoor air is excess carbon dioxide and water vapor, but thousands of contaminates, far too numerous to identify here, may become concentrated in the home.

The best way to determine if you have a potential problem would be to have your home tested with a ‘blower door”. The basic idea is to close up the house, and install a powerful fan in a door to the exterior to blow air out of the house. Sensitive pressure gauges measure the depressurization in the house that occurs as you blow the air out, and measure the volume of air moving through the fan. A blower door test typically depressurizes the house to a set negative pressure. The resultant air infiltration rate is roughly the same as if the house were subject to wind speeds of 20 miles per hour from all sides. This result, measured in cubic feet per minute, is then used to calculate air changes per hour.

If the house is found to be too tight, an air to air heat exchanger can be installed to bring in a set amount of fresh air to make up the deficit. The incoming air can be ducted to be evenly distributed in the house, and would be pre-warmed in the unit’s heat exchanger by the air that is being exhausted from the house. It may seem counter-intuitive to deliberately bring in air that you have attempted to exclude by sealing up the house, but the air you bring in through the heat exchanger will be less expensive than air that enters due to leaky windows and walls, because it will pick up heat from the outgoing air that would otherwise be lost. And it will be evenly delivered, only as needed. A blower door test usually costs only a few hundred dollars, and can give you valuable information to protect you and your family from illness due to poor air quality.

I want to lower my heating bills, which I am afraid are going to be outrageous this year, but don’t know if I should be adding more insulation, or replacing the furnace. Is there any rule of thumb guide to determine which is better?

There really aren’t any simple rules to help us decide which upgrade to make first to reduce our heating bills because specific circumstances can vary so widely. Generally speaking, however, if the insulation in the attic is under 6-8 inches thick, upgrading should easily be cost effective under most circumstances. If the heating equipment is over 40 years old, it’s a pretty good bet that upgrading to a high efficiency unit will be well worth the investment.

Since we are basically looking for a return on investment, you should look at the inexpensive improvements first. An amazing amount of heat loss occurs due to air exfiltration; in other words, warm air escaping the house because of poor sealing. Correcting poorly sealed components in the house is usually inexpensive. Some of the culprits that we often find while inspecting homes include poorly sealed attic doors or access panels, whole house fans without winter covers, suspended ceilings below attic space without a sealed ceiling above, cracks or gaps in ceiling finishes, especially in closets, open chaseways around chimneys or plumbing vent pipes, fireplaces with poorly sealed, missing or open dampers, older unsealed recessed lights, poorly mounted ceiling fixtures of any kind, kitchen and bath ventilators that don’t fully close when not being used, and the obvious poorly sealed windows and exterior doors.

Just because you don’t feel cold air coming in doesn’t mean that warm air isn’t escaping. Take the time to look around your house for potential points of heat loss. These can involve simple repairs, not requiring major upgrades and can save you a lot of money. You may need more insulation and a new furnace, but don’t forget the little things that can save a lot.

Last year I discovered mildew growing in my attic. I was told that I needed to ventilate the attic better, so I had a ridge vent installed. Now the mildew is worse than ever. What should I do?

The basic process that is occurring in your house is very common. We produce large amounts of moisture just living in a home. In addition, excessive moisture can be generated from less common sources such as wet basements, leaking pipes and blocked natural gas appliance vents. This warm moisture laden air in your house is rising by a natural process called stack effect, the same force that causes chimneys to vent, and hot air balloons to rise. The air in the living space of your house finds its way slowly into your attic, where it cools in winter. Cold air cannot hold as much moisture as warm air, so the moisture condenses onto the coldest surfaces, allowing the growth of mildew and mold.

There are three solutions to this problem. Reduce the amount of moisture produced in your house, prevent the moisture from getting into the attic, and better ventilate the attic. A home inspector can do a good job of finding the moisture sources and advising you on the means to correct them. An insulation contractor should be adept at finding the ways in which the living space air sneaks into your attic and sealing them. These include poorly sealed attic access doors, poorly sealed or improperly ducted ventilators, recessed light fixtures, plumbing and chimney chaseways, and the holes in the framing created to accommodate electrical wiring. You have attempted to solve the problem using the third method, improving the attic ventilation, but you may need to address the other two.

Also, your attempt to improve the attic ventilation may have been misguided and may be aggravating the problem. If you only add ventilation at the top of the attic, or in other words the ridge, via a ridge vent, stack effect will actually pull more moisture laden living space air into the attic from the rest of the house. You need to also improve the soffit ventilation. Soffit vents are openings on the underside of the overhang of the roof, or eaves. This will allow exterior air to enter at the low point in the attic, which will then rise and carry the excess moisture in the attic out the ridge vent that you already added. By balancing the exterior air intake and outflow from the attic, you will be able to achieve significant moisture reduction and help prevent further mold growth.

I have a cathedral ceiling. Near the peak the sheetrock is bowing out and the seams are showing. I’m not sure if it’s water or what, but a bubble is forming. Ideas?

The most commonly used modern interior wall or ceiling finish is drywall, often referred to as sheetrock. When finished it provides a relatively inexpensive smooth paintable surface. Drywall is made of sheets of gypsum sandwiched between paper. Gypsum is a soft mineral that readily absorbs water, which further softens the gypsum and then weakens the paper. It is very vulnerable to water, and readily supports mold growth. Increasingly visible seams, dimples at nails, yellowing, and sagging are all signs of chronic moisture in the drywall. The ceiling damage you describe is almost undoubtedly due either to water intrusion or to condensation buildup. If the damage is confined to a relatively small area compared to the size of the ceiling, it is likely to be due to leakage from the ridge vent. The ridge vent is installed at the peak of the roof to allow excess heat and moisture in the ceiling space or attic to escape to the exterior. If it is a metal type ridge vent, it is susceptible to leakage at the joints between the pre-made sections. Leakage may also occur from loosened nails used to secure the vent. The bubble that you see may be caused by the stretching of the latex ceiling paint, much like a water balloon, as water builds up between the drywall and the paint.

Widespread and relatively even damage near the peak would indicate condensation buildup above the ceiling. This is a much more serious and complex problem, potentially requiring reduced moisture levels in the house, improved ventilation of the ceiling space, and an improved vapor barrier on the ceiling. Removal of the entire ceiling and proper reinstallation would probably be necessary if condensation buildup is occurring. In either instance, the problem should not be ignored. Ongoing moisture problems and resultant mold growth and damage can only result in increasing costs to correct over time.

My wife and I are having a debate on where added insulation should go in the attic storage areas off the bedrooms in our cape style house. There is already some insulation in the rafters.

This can be a somewhat tricky question to answer, combining issues regarding proper ventilation as well as adequate insulation. In addition, cape style houses, or any homes in which living space is built into what is essentially attic space, with sloped ceilings and kneewalls, are difficult to adequately insulate. This is due to limited access and limited space available in which to install insulation to modern standards. There are two basic rules of thumb to remember which can be helpful when deciding where to place insulation. First, always place the insulation tight to the living space. This means that it should be applied immediately behind any finished surface in a heated room. The insulation should not be installed in the roof rafters unless the ceiling finishes are applied directly to the roof rafters. Unfinished attic storage areas are cold in winter. There is no advantage in insulating a cold attic from the cold outdoors. Instead, always insulate the floors, walls, and ceilings that separate the warm interior from the cold attic. The second rule of thumb just reinforces the first. You should never be able to see the paper vapor barrier on properly installed fiberglass insulation. If you can see the paper, the insulation is either installed in the wrong location, or is facing the wrong way. In order to prevent condensation problems, the vapor barrier should be kept warm. This means it should be installed tight to the interior finishes of the living space, where you won’t be able to see it. Now there are two problems to keep in mind while adding or placing insulation. Cold attic space must be able to breath, to prevent condensation problems. Outdoor air should be encouraged to enter an attic from a low area such as an overhang, and exit high, such as at the peak. Make sure your added insulation doesn’t block this flow of air. Also, your added insulation and ventilation will make those attic spaces colder. Make sure you don’t have any exposed water pipes in those areas that might freeze.

We have a very well built older home with solid masonry exterior walls. We understand that the walls are brick and clay tile blocks. We would like to insulate the walls. How can we do this?

No easy or inexpensive solution exists for this condition. Interior surfaces can be firred out with 2 x 2 ‘5 and dense foam board insulation installed against the walls. One and one half inch foam would provide an R-value roughly equivalent to standard 3 1/2″ faced fiberglass insulation. This process involves considerable expense, however, especially when dealing with exterior openings such as windows and doors and may not be cost effective unless major interior remodeling is being contemplated in any case.

Remember that heat rises and the majority of your efforts to reduce heat loss should first concentrate on ceilings and air infiltration problems rather than exterior walls. If these efforts have been made and major remodeling can fit in the budget, then its probably time to insulate those exterior walls.