QI'm considering getting a whole-house ventilation system. I've heard the terms Energy Recovery Ventilation and Heat Recovery Ventilation used for these systems. Are they the same? If not, which one is better at saving energy?
For readers who aren't familiar with these systems, I'll explain that they remove stale indoor air and bring in fresh outdoor air through ductwork that is installed throughout a home. These systems save energy in the wintertime because they transfer heat from outgoing air into incoming air.
As for your question: Energy-recovery ventilation systems (ERVs) and heat-recovery ventilation systems (HRVs) have one key difference. While both recover a portion of the heat from outgoing air, an ERV also recovers moisture. Due to this difference, ERVs can have higher efficiency ratings and HRVs are able to remove more moisture from a building.
Because of the potential for moisture-related problems in buildings, including wood rot and allergens like mold and mildew, it's important to consider more than energy efficiency when choosing between an ERV and HRV. One of the primary functions of ventilation is to remove moisture, so an HRV is likely to be the appropriate choice in our climate unless a space needs a significantly high amount of ventilation. In a case like this, an ERV can do the job without excessively drying out the air.
In either case, the efficiency of the motor has a big impact on energy use. Ventilators with variable speed brushless DC motors (sometimes referred to as ECM motors) will use considerably less electricity to operate than models with standard motors. A contractor specializing in heating, ventilation, and air conditioning (HVAC) can tell you more about these systems. Best of luck!
QI want to take your column's advice about fixing drafts and air leaks in my house, but I'm concerned that I'll eliminate fresh air. I've got sensitivities to lots of household things like cleaning products, new materials, mold, etc. What do you tell people who need fresh air and want to be energy efficient?
I let people know that saving energy and providing good indoor-air quality lie on the same path. As you're well aware, indoor air can contain pollutants like the ones you name and more. Moisture is also present in every home and can cause the growth of mildew and mold, which not only can be a health problem but also can damage the house itself.
Unfortunately, air leaks don't eliminate these problems and can significantly add to energy costs while creating uncomfortable drafts. Air leaks also allow air to enter your home through gaps in insulation and in the building. This may bring dust and other potential allergens into your living space. The good news is that you can lower energy costs, reduce drafts, and improve indoor air with the same approach: Air-seal and insulate the house and then install good, mechanical ventilation to reliably remove indoor-air pollutants.
A Home Performance with ENERGY STAR®contractor can find and seal air leaks throughout your house and then can install insulation. As for ventilation, you can get good results with an ENERGY STAR qualified bath fan, which uses very little electricity and runs quietly. Also, use a kitchen fan to remove moisture generated by cooking. Always vent bath fans to the outside and, if possible, vent kitchen fans outdoors too.
In case you're prepared to make a larger investment in the quality of your indoor air, I'll mention the existence of whole-house, heat recovery (or energy recovery) ventilation systems. These systems allow you not only to remove stale indoor air but also to bring in fresh, outdoor air. And this is done in an energy-efficient manner. You see, these systems save energy in the wintertime because they transfer heat from outgoing air into incoming air. A contractor specializing in heating, ventilation and air conditioning (HVAC) can tell you more about these systems. Best of luck!
QIn your column, you recommended ENERGY STAR® bath fans for saving energy. Isn't the best way to save energy to just open the bathroom window?
In ideal conditions, sure. Unfortunately, those conditions aren't available every day or in every home. Some bathroom windows are positioned on a side of the house or in relation to other windows in a way that doesn't provide sufficient air exchange. Sometimes, the humidity outside isn't lower than inside, or the outside air is still. And on most winter days, you could pay more to heat the air coming from an open window than it would cost to use a bath fan.
My advice is to take as much control over indoor air as possible to prevent problems that excess moisture can cause. Those problems can include unhealthy indoor air from mold and mildew, costly wood rot, and more cosmetic problems like damage to paint. ENERGY STAR qualified baths fan are energy-efficient, run quietly, and give you the ability to effectively control the airflow in your home. If you decided to install one of these fans, you can ask the folks at your local hardware store if they stock them or if they'd order one for you.
A: You're wise to address the problem of ice dams, not only because they can damage your roof but also because they're a sign that the heat in your house (which you pay for) is escaping into your attic. The way to prevent ice dams isn't to bring heat into the attic but to keep it from reaching the attic. In other words: A fan is not your solution.
I'll explain: Ice dams form when heat escapes into your attic, warms the underside of your roof and melts snow, which trickles down to the cold edge/eave, where it freezes. So, keep the heat in your house! That's done by a thorough job of sealing anyplace where air can escape from the heated house into the attic and then making sure that you've got at least 12 inches of well-installed insulation on the attic floor. Likely places for air leaks include attic hatches, pull-down attic stairs, the attic floor above pocket doors, gaps around plumbing and wiring and more.
The safest, most accurate and comprehensive way to seal air leaks is to hire a professional. A Home Performance with ENERGY STAR® contractor can use diagnostic equipment to find air leaks. The contractor can then fix the leaks and perform any necessary insulation work. You can a specially trained, certified contractor by calling an Efficiency Vermont specialist at 888-921-5990.
QWhat can I do about mildew that is taking over my bathroom even though I've repainted several times?
A. I bet you wish there were a quick and easy answer to this, but tackling mildew takes a little effort. When it comes to mold and mildew, bathrooms offer the perfect, moist environment. If you have a mild mildew invasion, you can clean the affected area with a diluted solution of bleach and prime it with a mildew-resistant sealer before painting it again.
It sounds like your problem may be more serious. Your first step should be to eliminate the source of the moisture if there are any leaks, but you might also have a ventilation problem. Does your bathroom have an exhaust fan? It should, and if you hold a square of toilet paper up to the intake grill, the paper should stay there when the fan is on. If it doesn't you have a problem with either the fan or the ductwork. Ductwork should be smooth-wall, not the corrugated flex duct, and vented to the outside. If you need to replace or install a fan, choose a quiet one (less than two sones, the unit that measures sound), and less than 50 watts that meets the guidelines of the Vermont Residential Energy Code. All ENERGY STAR labeled fans meet the code guidelines. Operate the fan as much as necessary to control humidity and always run the fan after showers until the walls are dry, which could be several hours.
A properly working exhaust fan should help solve future problems, but you may also need to take care of any mold that may have established itself. For more information on mold contact the Vermont Department of Health at 1-800-464-4343 or visit their mold reference page.
QOther than using a dehumidifier, what can we do to help dry out our wet basement?
A. There are lots of things that can cause a wet basement. In fact, I could write a whole article just on this topic. But let's start with the simplest reasons:
The first thing to check is that water drains away from your house. The exterior grading (ground) should slope away from your house so water runs away from the foundation. Sometimes water will leak in when it never used to because the gutters or drain spouts are plugged and water off the roof saturates the ground too close to the house. If you have gutters, check to make sure they're clean and that the downspouts extend away from the foundation by at least two feet.
If your ground is sloped and all gutters are in working order, a high groundwater table may the culprit. One fairly easy way to tackle this problem is to install a sump pump which draws water from beneath the slab and pumps it away from the house. The pump sits in a hole, or sump, that extends below the slab. When water collects in the sump, the pump turns on automatically and removes the water through a discharge hose that exits the basement above grade. Just make sure the hose ends several feet away and downhill from the foundation or you'll be pumping the problem right back in!
A. Never underestimate the power of ventilation in a home. Ventilation removes and dilutes pollutants, provides fresh air and may improve the durability of your home.
Exhaust ventilation, which is what happens when you run the bathroom fan, is a good ventilation strategy. Air that's pulled out of the bathroom causes replacement air to be drawn in through the small holes that are distributed throughout your home's structure. This diffuse introduction of fresh air means that a single fan can often ventilate the whole house. Just as important, removing bathroom moisture before it migrates around the house means you can reduce problems with window condensation, mold, mildew and other threats to a building's longevity.
It's true that you lose some heat and use some electricity by running the bathroom fan, but at today's energy costs, it's probably less than $100 for the whole year, even if you leave the fan on 24 hours a day. I'd call that a pretty good bargain for fresh air.
QMy bathroom fan is really noisy. Is that a sign that it's wasting electricity?
A. If you can hear the fan throughout the house - or even in nearby rooms - when you use it, chances are it's an energy hog.New energy-efficient fans are generally quiet. It's important to have proper ventilation to help maintain good indoor air quality, so leaving the fan off isn't a good solution. Instead, look for a fan that uses less than 50 watts and has a noise level of less than two sones, the unit that measures sound. This information is available on the fan and in the literature that it comes with it. You'll want a fan that you won't notice in the next room or on your power bill. All ENERGY STAR labeled fans meet the recommended wattage and sound standards.
QAre there energy-efficient dehumidifiers?
Yes. Look for an ENERGY STAR labeled dehumidifier. It removes the same amount of moisture as a similarly sized standard unit, but uses 10 to 23% less energy. These are high quality units which have more efficient refrigeration coils, compressors, and fans than conventional models. Over the lifetime of a machine, savings can add up to about $200.
QI've heard that dehumidifiers can use a lot of electricity. Is this true?
A. The short answer is, yes. But as with most energy-related questions, it's not that simple.
Running a dehumidifier in a wet basement, for example, could cost you as much as $31 a month. However, if you'd like to replace an older dehumidifier or are looking to buy a new one, look for the ENERGY STAR. Newer models have more efficient compressors and use considerably less energy. Here are some things to keep in mind about using a dehumidifier:
- Dehumidifiers are only effective for controlling humidity in an enclosed area and need to be sized appropriately. ENERGY STAR can help you choose the right size or give us a call.
- Contrary to popular belief, if you're trying to dehumidify a basement during the summer, keep the windows closed.
- If humidity in your living areas is a problem, a properly sized air conditioner can be more effective and energy-efficient than a dehumidifier. Again, keep the windows closed.
- The best way to control humidity is to track down and reduce or eliminate the sources of moisture.
- In the winter, use exhaust ventilation.
A: A good fan won't use a lot of electricity, but ventilating the basement will probably make your basement wetter. You see, when you put a fan in a basement window and set it to exhaust air out, you'll draw in air from other areas of the house or from the outdoors. If air from your living spaces is higher in humidity than your basement, its moisture content will condense on cooler surfaces, resulting in a wetter basement. The same phenomenon can occur if warm, moist, outdoor summer air enters a cool basement.
The way to keep airborne moisture out is to keep the basement as closed to the outside as possible. Seal basement vents and windows and even insulate windows if you don't need the daylight. Make sure that any basement doors to the outside fit well and have weather-tight seals (bulkhead doors are not airtight).
If, however, the moisture in your basement isn't coming from the air but from the ground, you have a bigger job on your hands. Speak to a contractor, who specializes in foundation building/rebuilding, about addressing the drainage outside of your foundation. Typically, this job entails re-grading the ground and installing rain gutters and proper foundation drainage. It's an expensive project, but one that will mean a dry basement, a longer-lasting house, and healthier indoor air.
