Issue 233 - Feb/March 2013 By now, most conscientious builders and designers know that ducts, furnaces, and air handlers belong inside a house’s conditioned space. Researchers have shown that ductwork in unconditioned attics or vented crawlspaces wastes about 20% of the output of a furnace or air conditioner. If the duct system is unusually leaky and poorly insulated—or as occasionally happens, if some of the ducts are crushed, ripped, or completely disconnected—the energy waste will be far higher. The furnace or air handler’s location determines where ducts should be installed. The best locations for ducts are in insulated basements, sealed crawlspaces, or unvented conditioned attics. If these places won’t work, ducts can be installed in openweb floor trusses or in some type of soffit, dropped ceiling, or chase. If you are building a two-story house with a centrally located mechanical room, it often makes sense to put ducts in open-web floor trusses. Follow these steps:• Any duct leaks will pressurize the joist bays, so be sure to air-seal the rim joist carefully to keep conditioned air indoors.• Order joists at least 16 in. deep to make room for insulation and ductwork.

Account for this when designing stairs.• If you are building a tight, well-insulated house with high-performance windows, locate supply registers near the center of the house instead of at the perimeter. This will keep duct runs short.• Communicate and coordinate with the HVAC contractor, the plumber, and the electrician. These subcontractors will all be competing for the same joist space.Pink Washer And Dryer For Sale Make sure that duct chases don’t have any leaks or air pathways that communicate with the outdoors. Does Laminate Flooring Work In BasementsBefore any ducts are installed, the chases need to be lined with an airtight barrier—for example, drywall, plywood, or OSB with sealed seams.Seat Belt Covers Ebay

In a single-story home, it often makes sense to install ducts in soffits or in a dropped ceiling. This design works especially well in a house with a central hallway flanked by bedrooms on both sides. In a house with a more complicated floor plan, duct soffits can be built along the top of any wall. If the house is designed with 9-ft. ceilings, there will be plenty of room to lower the ceiling height where necessary. For this approach to work, you’ll need to air-seal the soffit before the ducts are installed. If the drywall crew can’t come to the site twice, the soffit will probably be sealed by the framers with OSB and caulk. If this step is done poorly, however, the house will have a major air leak. It’s possible to order special roof trusses, called plenum trusses, designed to accommodate a duct chase near the attic floor. The resulting chase is variously called a raised HVAC coffer and an inverted soffit. In a house that has an 8-ft. ceiling, these special roof trusses make more sense than site-built soffits.

Like a site-built soffit, a chase within a roof truss must be air-sealed carefully before the ducts are installed, which means either that the drywall hangers and tapers have to come to the job site twice, or that your framing crew has to be trained to do the required air-sealing. These roof trusses create a bump in the attic floor, complicating the work of the attic-insulation crew. The chase’s walls may be vertical or sloping; in either case, protect the insulation on the walls of the chase with an attic-side air barrier. In years past, it was commonly assumed that as long as ducts were installed inside a home’s conditioned envelope, you didn’t need to seal the duct seams. These days, however, most energy consultants insist that HVAC contractors seal duct seams with mastic, even when all the ducts are inside the conditioned space. There are at least two good reasons for this practice. First, if ductwork is leaky, remote registers may get insufficient airflow, leading to comfort complaints.

Second, duct leaks in soffits or joist bays can pressurize these hidden compartments, forcing conditioned air outdoors through cracks in the rim-joist area. Placing your ducts indoors has several benefits:• It may be possible to downsize the air conditioner and furnace, which saves money.• Room-to-room temperature differences will probably be reduced, which improves occupant comfort.• Energy bills should be significantly lower. In spite of these obvious benefits, bringing the ducts inside the conditioned envelope is usually a headache for the builder, and the necessary details raise costs. Open-web trusses will probably cost more than I-joists, and deep joists may require a longer stairway. For a successful job, the general contractor will need to budget time for facilitating coordination between all of the trades, including the framers, the HVAC contractor, the plumber, the electrician, and the drywallers. Get home building tips, offers, and expert advice in your inbox

Secret DoorSecret DoorKristin at My Uncommon Slice of Suburbia created a shabby chic cover for her garage door opener using just an old frame, a hinge, scrap wood, and a crystal knob.Get the tutorial here » Custom CharmCustom CharmDon't let builder-grade air vents cramp your home's style. Tricia at Simplicity in the South covered hers using a decorative metal radiator screen from a hardware store. 8 Kitchen Makeovers That Will Make You Swoon Remember that article I wrote about ducts installed against the roof deck and how I said it was probably the absolute worst single location for installing ducts?  Well, in the comments, Dave Roberts, a senior engineer at the National Renewable Energy Lab (NREL), wrote about a paper he co-authored last year and included a link to it. Up against the deck may be the worst place in the attic to install ducts, but Roberts shows that putting them in the attic at all is the worst place in the house you can install ducts. The report, Ducts in the Attic?

What Were They Thinking?, summarizes the research that's been done about putting ductwork in unconditioned attics and basically says it's about the stupidest thing we do in homes that do a lot of air conditioning. I encourage you to download and read this report. If you're building or remodeling a home, make sure the general contractor (if it's not you) and the HVAC contractor get copies. I love the analogy they use to introduce one of the main problems with this location. "Heat exchangers," they write, "are designed to transfer as much heat as possible from one fluid to another." Comparing this configuration to a solar water heater, they make the case that putting air conditioning ducts in a hot attic is an effective way to heat up the conditioned air as it travels from the air handler to the conditioned space inside the home. If you've studied heat transfer at all, you may recall that the rate at which heat moves from a warmer to a cooler body depends on the temperature difference, which we abbreviate as ΔT.

An attic can get up to about 130° F in the summer, and the conditioned air entering the ducts is about 55° F or so. With hundreds of square feet of ductwork surface area in the attic and a ΔT of 75° F, the air coming out of the vents in your home will be significantly higher than 55° F. Throw duct leakage into the mix, and the problems are even worse. What Roberts and his co-author Jon Winkler did, in addition to reviewing the literature about this topic, was to model the savings possible when you relocate the ducts from an unconditioned attic to the conditioned space inside the building envelope. They chose Houston, Phoenix, and Las Vegas as the locations for their modeled houses. The table below summarizes the main results. In addition to comparing ducts in the attic to ducts inside the building envelope, Roberts and Winkler also looked at electricity savings of other measures, such as adding insulation, installing better windows, and using higher efficiency air conditioners.