Building Air Leaks & Heat Loss Analysis, Tools & Procedures
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• Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
  
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
  Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
• "Detecting Air Leaks", U.S. Department of Energy
• Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage

Basement Energy Loss Detected by Visual Inspection & Infra Red Scan Identifies Major Air Leaks in a Home's Basement

In the basement the crew find and seal the bottom of a plumbing chase and a missing window that was concealed behind a makeshift wall panel. A coal chute is found and sealed. See BASEMENT HEAT LOSS for more details.

We -DJF- recommend investigating and correcting building moisture sources such as wet or damp crawl spaces and basements. We have found this same convection current moving moisture and air between a wet basement and the attic in interior partitions both in older homes and even in brand new modular homes whose mating-walls were not sealed against such air-flow. See MOISTURE CONTROL in buildings. for more details.

Where both top and bottom of leaky interior partition walls or modular home mating walls are accessible, we seal at both ends in leaky homes.

Un-wanted Air Movement in Duct Systems

With the building pressurized using the blower door, a smoke test in this home showed air movement into a heating supply duct. The duct system should be a closed circuit, with the same induced pressure (from the air handler unit) throughout - a difficult leak to seal in an older home whose ducts are concealed in finished floors, walls, ceilings.

In other buildings we -DF- have found major duct leaks such as a partially or even entirely disconnected duct sections blowing warm air into the crawl space instead of the living room, or blowing cool air into an attic knee wall space instead of the bedrooms below. On a hot summer day the coolest place in that last home was inside the attic knee wall space! Look for major duct leak defects such as these, or if installing new HVAC ducting, be sure that the ducts and all connections are properly routed and sealed.

See LEAKY DUCT CONNECTIONS and DUCT SYSTEM DEFECTS, problems with the air duct system, air filters, supply registers, return air registers, for more details on tuning up HVAC air ducts.

Air Leaks & Energy Loss Points in the Living Space of a Home: cold corners, closets, kitchen soffits, plumbing chases, windows

In the house proper, occupants may already be aware of a "cold corner" in a bedroom or a closet on an exterior wall that often suffers from recurrent mold growth. Air leaks through kitchen cabinets and interior soffits can be very significant heat loss points in buildings. An infrared scan or invasive inspection can identify this energy loss location. Sealing the connection between the cabinet soffit and the building's exterior wall reduced building air leakage by 20 percent at a townhouse investigated by the experts in the original article given here. The sketch at left demonstrates how a kitchen soffit can become a heat pump, moving warm air (red arrows) and heat into a cold attic space while bringing cold air down into the living area. A small soffit over a kitchen cabinet may not look like much until you discover that it is drawing air from all kinds of wall and ceiling spaces. Leaky exterior door thresholds were found and sealed in this home, and air leaks around a second floor plumbing access panel were found and sealed as well. Addressing leaky windows can be a major expense if window replacement is being considered. The opinion of the energy savings crew for the home studied in this article was that only 30 to 30 percent of air leakage is at windows in most cases: the crew goes after the 70 to 80 percent of leaks that in their view "... must be coming from elsewhere". [OPINION-DF: we're not sure that these percentages are accurate for many homes, and we suspect that a combination of air leaks and single-glazing makes windows on homes a dominant energy loss problem second only to uninsulated homes with empty wall cavities and attic floors.] But we agree [DF] that before replacing windows on older homes there are steps that can significantly reduce air leaks at those locations: On other buildings we have had success with simpler measures such as finding and sealing air leaks around window frames and trim. In a slightly more aggressive measure for curing window leaks, we removed window weights (that move up and down in a hollow cavity along side window frames in older homes), insulated those spaces, and installed new window tracks whose spring-loaded sides permitted windows to be opened and shut safely and snugly. Installing high quality storm windows over older leaky window sashes can also be cost effective. But in the home studied for this article, even before considering the large expense of window repair or replacements, sealing the other leaks discussed in this article reduced the air infiltration rate by 25 percent.

Find These High Priority Targets & Hidden Leak Points to Save Heating & Cooling Energy Costs

Beyond simple caulking and weatherstripping, it is important to look at the whole building - moisture and moisture sources, air quality, heating and ventilation equipment, and HVAC controls - in order to determine what steps will be most cost-effective in saving energy for that particular building.

In older, multi-family buildings with primitive heating controls, shell tightening may fail to lower fuel costs if indoor temperatures are quite uneven between building areas.

If after weathersealing, the tenants on the south side of a building get too warm (during the heating season) and respond by opening their windows, that effect increases the drafts and convection currents in the building, making other areas (and tenants) too cold. The cold tenants turn up their thermostat even higher. The correct solution may be a more intelligent heating control, and possibly insulation between the tenant areas.

We -DF- see this problem particularly in two-story multi-family homes with an upstairs and downstairs tenant and a single heating system with a single thermostat located on the first floor. The upstairs tenants are too hot and the downstairs tenants are too cold. Slowing warm air movement between floors by insulation and sealing may be helpful, but an optimum solution includes separate heating zones and zone controls, or even separate heating systems entirely, permitting accurate heating cost apportionment among the tenants. In Europe BTU monitoring and accurate heating cost apportionment among tenants is required by law.

Air leaks at Attic Hatches, Attic Stair Tops, Whole House Fans

As the PEP pair of photographs show at left, viewed through an infrared scanner, hot air leaks (light colored areas in the left-most photograph) show up around the attic hatch (recognizable in the photo at immediate left) and within the top of the hall end partition. This thermogram was taken in summer with the house depressurized.

Air leaks at whole house fans can be very significant heat loss points in buildings as well, as our photograph at left shows. Failing to provide an effective cover for a whole house ceiling-mounted fan in the uppermost ceiling of a home is about like leaving the upstairs windows open in the dead of winter. But be careful not to remember to remove the fan cover before turning on the fan again in hot weather, or disaster, even a fire, could result. Insulation voids are distressingly common in attics even where lots of insulation has been installed. Sometimes it's an installation error, more often the voids occur when someone performs wiring or plumbing work and fails to replace insulation that was removed. Insulation voids also pump heat to the cold attic and thus to outside.

Convective Air Loops & Leaks - Thermal Bypass Leaks in buildings

The energy contractors claim that their work consistently saves the homeowner considerably more money than is predicted by the reductions in air infiltration alone. This seeming magic is attributed to the elimination of "thermal bypasses", that is, the myriad ways heat gets out of the building other than through wall and ceiling components following the rules and regulations of ASHRAE.

Prominent among these heat leaks are convective loops - wall and ceiling cavities that act as room-sized heat exchangers, relentlessly pumping heat out of a building even if there is no direct air leakage from indoors to outdoors.

Our photo (left) shows the black stains deposited by dust particles (this is not mold) when building air leaks past fiberglass insulation, seen from the attic side of a 1960's contemporary framed home with lots of air leaks. In our photo and in many air leak problems at fiberglass-batt insulated cavities, the problem is one of installation and construction leak problems, not a defect in the fiberglass insulating batt itself. See Air Bypass Leaks, Thermal Tracking for details.

The claim of fiberglass batt air leakage, supported vigorously by the foam insulation industry, is equally vigorously counter-argued by the fiberglass insulation companies who point out that properly installed the air flow rate through the fiberglass itself in fiberglass insulated cavities is very low.

Where air leaks occur around fiberglass batts, look closely: you will probably see that the leaks are at the perimeter of the insulation and at locations where openings in framing, drywall, or insulation were cut to admit recessed ceiling lights, electrical or plumbing penetrations, or similar openings. If airflow were simply through the fiberglass batt in any uniform way, the dust stains on and inside the insulation would also be expected to be uniform. They are not.

We full agree with PEP, however, that predicting air leaks through fiberglass-insulated cavities is very difficult, since leakage depends on the quality of installation workmanship. We have indeed occasionally found workmanship errors that resulted in unanticipated air leaks though foam-sprayed insulation as well, particularly when the insulation (of either type) was installed in a hard-to-access space such as a crawl area.

Our pair of photos above were taken in a tight, hard to enter crawl area where the icynene spray foam insulation was not so carefully applied. Our smoke test found air movement from the damp, occasionally moldy crawl area into an opening in the foam insulating blanket. We pulled a bit of this already-leaky material off to see what was behind and found (photo above right) a leaky metal return air duct. When the air handler was running it was drawing cold, sometimes nasty, crawl space air into the duct system through this leak.

Estimating convective loop heat losses

In addition to their effect on energy bills, the impact of convective loops in buildings can be gauged by measuring attic temperatures before and after sealing off thermal bypasses such as chases and wall partitions, or it can be roughly modeled from the temperature difference and the height of the convective loop.

Stacked Bathrooms & Plumbing Chases Form Convective Loops

In multifamily and even single family buildings it is common for bathrooms to be "stacked" one on top of the other, forming a giant convective loop. In many cases PEP (the energy consulting and weatherizing firm in the original article) finds interior partitions colder than outside walls. Since the cooling effect of a convective loop is only partly due to air leakage, even a completely closed wall cavity such as a (hollow core block) masonry party wall can cause problems. One cure in the case of a masonry party wall is a solid course of block at the ceiling level, isolating the airflow within the heated space. Of course this is most easily accomplished during new construction.

The Bottom Line on Energy Retrofits Using Caulks and Sealants

Energy retrofitting reduces drafts and cold spots and, according to PEP, produces some unanticipated benefits such as fewer rodent problems and fewer frozen pipes. Still, to sell the service to big buyers - the developers, housing authorities, and government agencies - it has to show an attractive return on investment. Says Gadsby referring to conventional weathersealing treatments, "To do a job for $1200. that's going to save $50. a year is just not the way to do business."

In some cases the savings have been spectacular. For example in a 1982 retrofit, PEP spent three months retrofitting the 450-unit Glenhardie Condominium Comlex near Valley Forge, PA, for $62,000. The 20-building development already had its insulation and heating system upgraded when it went condo four years earlier. After three months of house-doctoring, consisting solely of attic work, the annual heating bill was reduced from2093 to 1329 therms of natural gas, resulting in a first-year savings of $40,600, not including the $9,300. tax credit.

More typical was a proposal to the Baltimore Housing Authority, in which PEP agreed to treat apartments for $550. each while they were undergoing rehab. PEP's work was to be staged over two to three visits. With annual heating bills in that housing stock running $1200 to $1300 (1984 costs), the simple payback would be under three years. In terms of air infiltration alone, said Gadsby, recently-built townhouses generally measure in at about 10 to 15 ach (1984 data) at 50 Pascals before house-doctoring and are sealed down to about 6 ach after.

Costs for weatherizing are held down by providing the service in a one-day blitz, or in new construction in a series of quick hits. In general, a weatherization company can do more effective work for less money during construction or rehab than with retrofitting, since the problems are more visible and accessible. The cost to the homeowner was estimated to be one half to two-thirds what it would cost to retrofit after construction, and you're probably going to save an extra 5 to 10 percent on energy costs as well.

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

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