Closed Crawl Spaces. Applied Building Science Team Cyrus Dastur. Presented to the NAWSRC, July 2006

Transcription

1 Closed Crawl Spaces Applied Building Science Team Cyrus Dastur Presented to the NAWSRC, July 2006 Advanced Energy ABS Team High performance home programs Training and process consulting Failure diagnostics Applied building science research Not an installer Not a manufacturer or distributor 1

2 Why care about crawl spaces? Large scale problems With serious impacts! Homeowner complaints Clients with failure and liability New homes failing Existing homes failing Uncomfortable humidity Mold growth or musty odors Condensation on insulation, ductwork, piping, etc. Buckled hardwood floors Rotting framing Structural failure Goals Crawl spaces need improvement There are feasible ways to improve Can this benefit your customers and your business? What has AE learned in NC that can help you implement or improve? 2

3 Agenda What s wrong with vented crawl spaces? The physics of air and water vapor Research results Building codes and closed crawl spaces Break Key design and installation issues Q & A, sharing experience * Resources PDF of this presentation is available Book & reports are at 3

4 Regions Represented? IRC 2000, Figure R301.2 (7) Probability of Above-Ground Decay So what s wrong with typical code-compliant vented crawl spaces? 4

5 2004 Characterization Study (45 NC Homes) 2004 Characterization Study 67% of crawl spaces had WMC > 19% 22% had wood rot NOT caused by plumbing leaks 24% had wood rot caused by plumbing leaks Typical 6 x 12 hole to the house Stack pressure and HVAC driving forces Very high bioaerosol levels: Crawl spaces are MADD! Crawl RH June July Aug > 90% 56% 74% 72% > 70% 100% 100% 99% 5

6 Symptom: Light mold spotting in crawl space Typical response: Add ventilation 6

7 Resulting fungal explosion Some lumber is still good but some is completely rotten 7

8 So why isn t ventilation with outside air keeping crawl spaces dry? Water Vapor in Air Temperature and Relative Humidity Air typically contains a certain amount of water vapor Warm air can contain more water vapor than cold air Relative humidity = amount of water vapor actually in the air how much water vapor the air can hold at that temperature Condensation occurs if we add water until the RH = 100% Condensation occurs if we cool the temperature until RH = 100% 8

9 The Crawl Space Ventilation Myth 85 F 60% RH 70 F DP Framing: F 73 F 90% RH 70 F DP Ducts: F H 2 O pipes: F Floor: F Moisture Content of Wood in Equilibrium Relative Humidity 55% 60% 65% 70% 75% 80% 85% 90% Temperature (F) 50º 60º 70º Source: U.S. Forest Products Laboratory, Wood Handbook Table 3-4 9

10 So would it be better to keep outside air OUT of the crawl space? Or will we rot the building down? Field Study Site (12 Homes in NC) 10

11 Site Elevated for Flood Protection Experiment II: June Wall vented R-19 Floor Closed Sealed liner R-19 Floor Closed Sealed liner R-13 Wall 11

12 Closed Crawl Space Supply Air Duct 100 Phase II Crawl Space Relative Humidity Relative Humidity (%) Jun-03 Jul-03 Aug-03 Aug-03 Sep-03 Oct-03 Nov-03 Dec-03 Jan-04 Feb-04 Mar-04 Apr-04 Outside Wall Vented Closed 12

13 Summer RH Summary (Summer: June - August) Percentage of Time Vented Closed Vented Closed Above 90% RH 0% 0% 23% 0% Above 80% RH 39% 0% 86% 0% Above 70% RH 79% 0% 98% 5% Above 60% RH 94% 0% 100% 64% Above 50% RH 100% 100% 100% 100% Average Daily Crawl Space Temperatures Temperature ( o F) Jun-03 Jul-03 Aug-03 Sep-03 Oct-03 Nov-03 Dec-03 Jan-04 Feb-04 Mar-04 Apr-04 May-04 Vented + R-19 Floor Sealed Liner + R-19 Floor Sealed Liner + 2'' Foam on Walls 13

14 Phase II Average Wood Moisture Content W ood MC (%) Aug 2003 Oct 2003 Dec 2003 Feb 2004 Apr 2004 Jun 2004 Vented + R-19 Floor Closed + R-19 Floor Closed + 2'' Foam on Wall Seasonal Energy Use and Savings Thousands Season Summer Closed with Floor Insulated -22 % Closed with Wall Insulated -36% kwh Fall Winter -5 % -10% -10% +4% 2 1 Spring -19% -28% 0 Annual -15% -18% Jun-Aug '03 Sep-Nov '03 Dec '03-Feb '04 Mar-May '04 Vented + R-19 Floor Closed + R-19 Floor Closed + 2'' Foam on Wall 14

15 Field Study Conclusions CCS provides excellent moisture control CCS delivers significant energy savings with either floor or wall insulation in NC climate CCS is feasible to install and maintain Performance was achieved with designs that isolate the crawl space from the living space So what about the building code? (By the way, it wasn t based on science to begin with ) 15

16 Recap: Closed Crawl Space Key Components Liquid water management (exterior and interior) Sealed ground and wall vapor retarders Air sealed walls and subfloor Drying mechanism (nature vs. humans) Insulation (with pest management) Why call it Closed? Unvented vs. Sealed vs. Conditioned vs. Closed Building Codes IRC: Under Floor Space with Exceptions : NC Modifications (Nobody was happy) 2004 IECC Supplement and 2006 IRC Sealed floor vapor retarder, extend 6 up walls Reduced drying mechanism choice and volume (Exhaust, Supply, or Plenum; no D/H) Requires perimeter L-shaped insulation No termite inspection or wicking gaps Requires air transfer to the house No crawl space grading and drainage requirement No combustion safety requirement Retrofit vs. new construction 16

17 Let s take a break cdastur@advancedenergy.org There is No Silver Bullet Successful implementation requires: Process Design Training Product The crawl space is part of the house system. 17

18 Key Design and Installation Issues Combustion safety Fire safety Radon control Mold control Moisture control Pest control Drying Insulation Performance verification Worker Safety Combustion Safety Efficiency and safety consequences Beware of atmospherically drafted appliances Carbon monoxide poisoning Role of duct leakage Codes and confined spaces 18

19 Combustion Safety Ideally use direct vent appliances Combustion air interlock is an option Vent gas regulators to outside Provide raw gas leak detector/alarm Provide low-level CO monitor: Verify that tighter building doesn t cause backdrafting/spillage of combustion gases Combustion Air In-Forcer 19

20 Fire Safety Foam plastic insulation Storage in a closed crawl space Dow Thermax Fire Safety: Air Sealing Floor penetrations Ductwork 20

21 Radon Control Radon is a serious health risk Test to confirm need for radon gas mitigation Closed crawl spaces can accumulate radon Sealed liner does not eliminate radon Treat closed crawl like a short basement: Ventilation Reduces Radon Risk 21

22 Outside air intake Mold Control Mold needs air, food, and water We can control mold by controlling moisture Potential odor issues, stain residue Some clients will demand cleanup Foster s products for remediation Sostram Mold-RAM for new construction (requires pest control license) 22

23 Moisture Control Roof runoff managed Surface water managed Foundation waterproofing Proper site grading Flood vents where required: FEMA-NFIP Flood Vent 23

24 Moisture Control Sealed ground/wall liner material Plumbing leaks controlled - drains T/P or overflow discharges outside Condensate discharges outside Air sealing Hang and seal liner on wall 24

25 Air sealing of penetrations of the band joist or wall Pier Treatment Vapor retarder application to pier - Hilti Corp. GX-100-E? 25

26 Grade soil inside crawl space Raven Industries (Dura-Skrim) Reef Industries (Griffolyn/TX1200) Ground vapor retarder attached to drain intake grate 26

27 Separate foundation and crawl space drains Drain to daylight 27

28 Sump pump Drain termination protection 28

29 Moisture Control Nature is relentless and people aren t perfect! Closed crawl spaces need a drying mechanism Supply air duct for central systems (Famco, American Aldes) Dehumidifier (Therma-Stor or equivalent) House air injection Don t rely on duct leakage! Pest Management Termite view strip Access for inspections and retreatment Work with pest management contractor Pest Management Systems: Billy Tesh

30 Termite view strip Drying Existing Buildings What is the starting condition? Rate of drying Depth of drying Potential for damage Damage waiver 30

31 Insulation Local R-value requirements Retrofit considerations Non-absorbent insulation on walls Avoid L-shaped configuration Don t forget the crawl space door 31

32 Fastening Wall Insulation Existing Construction Dow Thermax Insulation Board Hilti DX-460-XIE Powder-actuated Nailer Fastening Wall Insulation New Construction 32

33 Performance Verification One measurement is worth a thousand opinions Carbon Monoxide Radon - home inspectors Temp/RH Annual service inspection, warranty renewal Performance Verification Data Loggers Online Logging and Monitoring In-home Monitoring Crawl Space Care Technology

34 Worker Protection Worker protection must be considered as part of the overall program Respiratory exposure Tool safety Conclusions Closed crawl spaces offer a range of major improvements to the safety, health, comfort, durability and energy efficiency of residential buildings We need to build support in building code bodies for closed crawl spaces (this might include explaining risk of liability) Researchers and private companies are investing time and $$$ to identify acceptable designs for different markets There is high market potential to deliver this technology Demand and supply It is easier than ever to steer builders and consumers to quality designs, products and processes 34

35 Thank You! 35