- Home Improvement
Cut Your Energy Bill and Save Money with These Home Corrections
Renewable Energy in the Home
Correct Construction Mistakes
This article can be viewed in full in the November 2007, edition 190 of Fine Homebuilding. "Home Remedies for Energy Nosebleeds" was originally published by Bruce Harley.
You may want to consult an energy consultant to review your home in order to check construction mistakes that are costing you your relatively high energy bill. There are many time savers in the construction of your home that may be what's causing the high bill, so by looking at how your home is built and its basic foundation, you may be able to cut your bill by at least one-third, if not more.
The most common construction mistake is leaving behind holes and gaps.
People think windows and doors are the biggest leaks in a house because windows and doors are the most visible holes. But even old windows, and doors are relatively small holes. In reality, the majority of energy leaks happen in places you can't see, where one trade's work ends and another's begins: behind drywall, up in the attic, or down in the crawlspace. Even when each trade does its job well, problems can occur because nobody sees the big picture. The way to work fits together is as significant as the work itself.
The gaps between trades usually translate into gaps in a house's thermal boundary. These gaps are addressed in current building codes, but building inspectors can't always offer protection. Sometimes they don't understand; sometimes they just don't enforce energy codes. The architect, general contractor, or homeowner must take he responsibility for understand and closing these gaps.
The two trades most concerned with energy efficiency (HVAC and insulation) rarely follow the widely published minimum industry standards for their work. The reasons differ, but they share one common element: their work is hidden behind drywall. The only feedback we get when these systems fail is comfort problems and high energy bills. Pressure to keep up-front costs low and underestimating the magnitude of the problems are also common to both trades. This standard of care isn't reasonable. Just because it has always been done this way doesn't make it right.
Mistakes in Framing and Architecture
Framers often construct large holes that extend from the basement to the attic in for the form of chimney, plumbing, and duct chases. These chases are hidden behind drywall or are covered by fiberglass-batt insulation. But insulation alone won't prevent conditioned interior air from escaping.Big holes should be sealed with plywood, rigid foam, or drywall and caulk or spray foam.
Kneewalls and rime joists are two more often missed examples. Think of them as long as holes in a house. Kneewalls are found in finished attics and bonus rooms above the garage. Insulation doesn't keep a room warm unless you block each joist cavity or insulate the roof deck. Rim joists also have myriad holes cut in them for dryer vents and outdoor water faucets. To seal rim joists, start when you build the house. Seal the top and bottom edges with construction adhesive during framing, and use spray foam afterward.
Architects use features such as cantilevers and wraparound porches to break up the massing of a mundane facade. These can be energy problematic.
Insulation and air-barrier details are often missed in cantilevered areas. The underside of a cantilever should be covered with sold sheathing, caulked in place, before finish materials are installed. Roof and wall sheathing is frequently left off below intersecting porch and garage roofs. The spaces below these roofs often connect to vented attics; they are just big air vents to the outdoors. Fancy details like tray ceilings and curved walls also can create big holes that open to attics.
Insulation, HVAC Ducts, & Air Handler
People tend to think that if you cover 98% of a surface with insulation, you'll get 98% of the performance. With insulation, however, this thinking is horribly wrong. Gaps missing insulation create a hugely disproportionate performance penalty.
For example, if you install R-38 batts in an attic but leave 0.5% of the surface area uncovered, you'll end up with R-32 (16% reduction in R-value). Leave 2% uncovered, and you drop to R-22 (42% reduction). So, with a 98% coverage, you get 58% of the performance.
If you run across information saying that it isn't cost-effective to add insulation, it probably assumes the initial R-value is what you say it is. In all likelihood, the R-value is less than half what you think, and the upgrade is worth much more, as long as it's done correctly.
From 20% to 40% of the air that comes out of furnaces and air conditioners never get to the rooms it's supposed to heat or cool. When you consider that most of the ducts are in attics, garages, and vented crawlspaces, the effect of that loss is huge. Sometimes whole rooms are disconnected, as when the duct work isn't connected to the register and the duct spews conditioned air into the attic of crawlspace. Return ducts often leak more than supply ducts, but although they cause less energy loss, these leaks cause moisture problems and pressure imbalances that pose health and durability risks by contributing to mold, ice dams, and even carbon-monoxide poisoning.
Required by code, duct-sealing is rarely completed and even more rarely tested. Houses more than 10 years old didn't have this code requirement. Every connection in every duct run should be sealed with mastic, and the system shouold be pressure-tested, just like your plumbing. Holes in the air handler can be sealed with aluminum-foil tape because mastic would render the cabinet unserviceable. After you seal the ducts and the cabinet, insulate them carefully.
Retrofits can be more difficult. If you can access the ducts, you can use mastic under the insultaion. If hte ducts are inaccessible, you can seal them from the inside with a product like Aeroseal, or you can move the insulation and the air barrier to bring the ducts inside the thermal boundary.
Also, consider that ducts lose up to 40% of the air if they are not properly sealed, so use a latex duct mastic to seal duct joints instead. Check for ducts that are covered with duct tape; these will commonly be those that are not sealed correctly.
Many air handlers and ducts are in attics. This location is a lot more costly than people realize. Putting an air handler and ductwork in the attic, garage, or crawlspace is like putting it ouside the house. Attics arealmost as cold as outside during the winter. In the summer, attics are much hotter than outside.
If you must place the air handler and ductwork in the attic, you can do a few things to minimize energy losses. 1) Seal everything with mastic. 2) Insulate the air handler carefully. 3) Keep the ducts low and covered with blown insulation. You may want to consider spray foam on the whole roof and gable ends so that the attic space is within the house's thermal envelope.
The best ida is to run the mechanical system inside the house. You can use smaller mechanical equipment with smaller ducts in shorter runs. With smaller ducts and shorter runs, it's easier to design space for them within the house. THe payoff is a much more efficient HVAC system that increases comfort while decreasing operating cost.
AC, Water Heaters, & Windows
Air Conditioning Systems
Oversize air-conditioning systems are the norm, not the exception. It's easeir to pick a huge system based on erroneous ruls of thumb than to spend time designing a more-suitable but smaller system. Oversize systems have the added problem of masking many problems discussed here. Poor insulation, duct leaks, and more can be covered up bby blasting twice as much cold air through the ductwork as would be necessary if things were done correctly.
If you double the size of the AC unit, you can lose 505 of the performance and still provide enough comfort to the home. But a behemoth AC unit short-cycles, which hurts its energy eggiciency, degrades its ability to dehumidify the air, and shortens its life. A larger unit is also noisier and costs more to install. The solution is simple- pay for the load calculations and size the unit correctly. In fact, according to the Air Conditioning Contractors of America, it's often better to undersize an AC system a little bit.
Water heaters store hot water all day long. They keep it hot on the off chance that you'll need it. Tankless, or on-demand, water heaters, on the other hand, convert cold water into hot water when you turn on the tap. Conventional water heaters wast about 40% of all the engery you pay for; tankless water heaters wast little.
You'll notice that windows aren't on this list. Only after you correct all the things mentioned so far will your windows start to look bad. Upgrading the windows at the designe stage to at least Energy Star is a lot less expensive than buying substandard windows now and replacing them later. Even so, windows are not usually the first place to start looking for big savings because the other construction concerns are running hard.
3 Ways to Cut Your Electic Bill Up to 20%
- Phantom loads (energy used by devices even if they are not on) can amount to 10% of residential electric bills. Phantom loads come from perpetually plugged-in transformers that recharge cell-phone and laptop batteris. They also come from electronic appliances like TVs and microwaves with standby mode or built-in clocks. While these devices can be unplugged individually, it's more convenient to use a power strip that feeds multiple loads. Plug the power strip into a switched outlet, and shut it off with a wall switch.
- Compact fluorescent lightbulbs (CFLs) can take another 10% off your electric bill. Replace any incandescent light used for more than an hour a day with CFL.
- Buy Energy Star- labeled appliances. Energy Star appliances are more efficeient than non-Energy Start rated models.
Save Money by Being Energy Efficient
- Remodeling Your Home to be Energy Efficient
When remodeling your home, you will want to consider these valuable tips that will save you money. Your home will be more energy efficient after the remodeling.
- How to Reduce Your Energy Bill and be Energy Efficient
Check out these simple tips and modifications that you can do to reduce your monthly energy bill by being more energy efficient around the home.
- Use Solar Energy to Heat Water
How to use solar energy to heat your home's water system. Find out ways to cut you energy bill by using solar energy.
- Tips to Correcting Tankless Water Heater Problems
Using a tankless water heater versus a tank-style water heater, you can save energy and conserve water. Remember saving energy can potentially reduce your energy bill.
Fine Homebuilding Magazine
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