Things To Do and Not Do When Weatherizing Southern Homes Doug Garrett, CEM Terry Brennan
Doug Garrett, CEM Building Performance & Comfort, Inc. Administered Austin Electric Conservation Association of Energy Engineers, Certified Energy Manager (CEM) Green Building Program staff for 5 years Air Conditioning Contractors of America (ACCA) Certified Instructor for A/C & Furnace sizing, Duct Design and Equipment Selection Several Indoor Air Quality - Mold Certifications Former Builder and Remodeler Home Performance Forensic Testing, Consulting, Specifications, and Training www.bldgperformance.com
Agenda for Today Building Science and Weatherization What Makes Sense in Southern Region What Doesn’t Make Sense
When We Say the South We Mean the Hot and Humid and The Mixed Humid Climates Zones. H&H zone has very little winter at all and M-H has brief periods of cold with mild times in between. You could throw in the Hot/Dry and Mixed/Dry areas too for that matter.
Do Not Assume That the attic and the crawlspace are outside of the house. Do not assume that it is best to make them outside in all cases or to bring them inside in all cases.
Do Make the Effort to Test/Define the Air Barrier Is the Basement or Crawlspace part of the Conditioned Space? Are there any dropped ceilings, furr downs over kitchen cabinets, or utility chases in the conditioned space? Does the Knee Wall and the Shed Roofed Porch have an air barrier behind them?
SUNPORCH FINISHED ATTIC LIVING SPACE BASEMENT F WH GARAGE Conditioned Space?
SUNPORCH FINISHED ATTIC LIVING SPACE BASEMENT F WH GARAGE Or Conditioned Space?
A/C & Ducts In or Out? If the ducts are in the crawlspace can we easily bring them into the conditioned space? Will it help solve other issues like decay of the home, critters living in the ducts or IAQ issues impacting the health of the occupants if we do?
The House Is A System Crawl Spaces: Generally It’s Best to Not Ventilate Them!! Outside Air Is Too Humid to Dry Anything most of the year - And it Just Freezes Pipes in Winter. Seal them air tight, use 6/10 mill vapor barrier on the dirt, insulate the stem wall and ventilate with conditioned air at 20 CFM/1,000 SF of floor. IRC 2000 (R-408) allows this method of construction. In retrofit, at least put the 6 mill plastic down covering the dirt!
EEBA Builders Guide Building Science Corp. Required in the South or no termite warranty!
Termite view strip or No Mans Land! Photo by the Healthy Building Company
Do Not Assume that It’s Really Insulated? Kneewalls, dropped ceilings, furr downs in kitchens and utility rooms may look insulated but are they? They often have a lot of insulation that is in storage waiting to be put to some useful employment in the future.
Do Take the Time to Address Thermal Bypasses Especially in the Attic
Do Not Assume That the A/C Is Sized Right Because They Say It Cools Most A/C’s are not right sized Our actions and the improvements we make change as in reduce the cooling and heating loads
Do Take the Time to Calculate the Right Size ACCA has developed the methods for over 40 years. They are really on target now. They are actually required in the building codes now!
HVAC Issues Replacing units with the same size that is there now. Not improving the ducts when you replace or repair a unit. Not sealing ducts when weatherizing a home.
Some Facts About Sizing ACCA studies show that the average A/C installed in the past 20 years is 150% to 200% bigger than it should be. A/C contractors have been held liable for causing mold and other indoor air quality problems in homes and buildings due to over sizing equipment or improperly addressing ventilation needs.
HVAC System: A/C Sizing: Rule of Thumb – Based on construction practices of the ’60’s! 1 Ton could only cool 400 to 500 SF Right for construction then, not always right for well weatherized homes today. Size by ACCA Manual J and Select Equipment by ACCA Manual S.
HVAC System: Manual S - Selecting equipment far over calculated load ACCA Manual S says to pick equipment that is Never More Than the Load in BTU’s + 15% Maximum! Take calculated load and multiply it by 115%. That is your maximum total equipment size.
Building Science for HVAC HVAC Role: Design to ACCA Manuals J8 & D required by 2006 IECC Install air tight ducts, mastic sealed Return Grilles – 200 CFM/SF Filter Grille or 300 CFM/SF Non-Filter Grille Use the right high efficiency filters
Building Science for HVAC Supply Ducts Equivalent Length = Long- 0.06”, Med.- 0.08”, Short- 0.10” W.C. Select equipment with a Sensible Heat Ratio (SHR) of 0.75 or less to control indoor humidity! Select equipment by ACCA Manual S, no larger than 15% over calculated load.
No moisture removal to the left of these points
HVAC System: Benefits The new A/C will operate more efficiently. The new A/C will deliver greater comfort. The new A/C will last longer with fewer repairs. The new A/C will improve the healthfulness of the home and the people living in it.
Ducts and all building chases and cavities used as ducts LEAK! Don’t worry, this is only a $2 Million dollar home just a week short of completion!
Do Not Assume That Ducts Are Tight Because They Look Tight I guarantee you that you can’t tell diddly squat about how tight ducts are by looking! You may guess right sometimes but then even a blind pig finds an acorn occasionally and that’s not reason to start bragging.
Do Take the time to Deal with Pressure Imbalances!! EEBA Builders Guide Building Science Corp.
HVAC System: In a 3 Month Accelerated Aging Test simulating 30 Years in the field, U.S. DOE found Failure in: –Cloth Duct Tape = 7 Days –UL-181B-FX Tape = 10 Days –UL-181 B-FX Foil Tape = 10 days –UL-181-A (metallic) and B (Flex) Mastic = No Failures!!
Static Pressure Should be... Less than 0.5”wc or 125 Pa. combined for both supply and return. Add the two readings and ignore the + and – signs. Measure after duct sealing is done. If it is too high, add ducts and grilles to ease resistance.
Storm Windows? Storm windows are not cost effective in the South. They are popular with many contractors because they are easy and they are profitable. If you live where the codes require Low E glass you should not retrofit homes with storm windows!
Solar Shading Is The Southern Equivalent of Storm Windows Installation of solar shade screens or solar film is cost effective when A/C is present. The Shade Coefficient should be 0.50 or lower. The measure must cover all of the glass area, not just the operable section. Permanently secure to the home.
Unvented Gas Space Heaters Try your best to replace them with vented units. At least replace them with units having an ODS. If you can’t replace it with a vented unit do not tighten the house or you can cause death or a moisture problem.
A Few Quick Do’s and Don’ts Tips and information to make it go smoothly.
What the heck is a U factor anyway? U factors = R value stated as a decimal R- 4 is fraction ¼ as a decimal it’s stated as 0.25 So, R- 4 = U- 0.25 R-10 = 1/10 = 0.10 as a decimal So R-10 = U- 0.10 Bigger R’s and Smaller U’s are better