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Subcommittee Lessons Learned

Residential Weatherization and Ventilation Subcommittee Ventilation Specification Proposed June 1, 2011. The value of the subcommittee is to make the investment to dive deep into the issues – and come up with a solution.

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Subcommittee Lessons Learned

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  1. Residential Weatherization and Ventilation SubcommitteeVentilation Specification ProposedJune 1, 2011 Subcommittee: Residential Weatherization and Ventilation

  2. The value of the subcommittee is to make the investment to dive deep into the issues – and come up with a solution. Ventilation is an important topic to many, but a lack of real data causes opinions and estimates to color the conversation. We don’t all agree, but willing to put in the time to format a reasonable solution. Look forward to more data and the revision cycle. Subcommittee Lessons Learned Subcommittee: Residential Weatherization and Ventilation Specifications

  3. Measures should not cause harm. Base the standard on ASHRAE 62.2. Avoid ventilation standards that preclude energy savings from air tightness measures. Be mindful of cost; the recommended path should be “doable” in utility WX programs. Avoid creating a threshold that allows air sealing to a “certain tightness” below which ventilation must be installed – don’t create an artificial stop point. Recognize interaction of spot ventilation and how it can contribute to overall ventilation as well as address IAQ in source locations. Deciding on a Ventilation Standard: Guiding Factors Subcommittee: Residential Weatherization and Ventilation Specifications

  4. ASHRAE 62.2 – Whole-House Ventilation Requirements(Existing Houses with blower door test results) Standard Ventilation Rate (Section 4.1) Infiltration Credit (Section 4.1.3) Local Exhaust Adjustment (Section A3) Subcommittee on Residential Weatherization and Ventilation Specifications

  5. 62.2 Is recognized (and required in DOE WAP programs) national standard but: • Isn’t perfect (by ASHRAE’s own notation) • Might over-ventilate “looser” homes, negating energy savings from air sealing measures • Might cost too much for homeowners, installers, and utility economics tests. Based on ASHRAE 62.2 Subcommittee: Residential Weatherization and Ventilation Specifications

  6. Option A – Require 62.2 (mostly) Option B – Use pre and post blower door tests to determine a “mitigation” level of ventilation based on 62.2 Option C – Require an equation-modified version of 62.2 A: 0 Votes B: 4 Votes C: 15 Votes Subcommittee Vote and Results Subcommittee: Residential Weatherization and Ventilation Specifications

  7. Untested operable spot fans may receive 25 cfm (bath) and 50 cfm (kitchen) credit. Justification: To simplify implementation by not requiring testing. Half credit for bath fans (25 cfm) provided based on subcommittee’s field experience testing existing bath fans. Kitchen fans follow suit. 1 Modifications to ASHRAE 62.2(proposed in all options) Less than 20 cfm “waiver”: If whole-house continuous ventilation requirement is less than 20 cfm, fan installation is not required. Justification: Take into account the imprecision of fan and leakage testing. Also, installation of a <20cfm fan doesn’t pass the “laugh test” regarding providing better IAQ. 2 Max ventilation rate: Installed equipment cannot exceed 150% of the prescribed rate. Justification: Avoid wasting energy by over-ventilating. 3 Replace code compliance of gas venting and chimneys with CAZ testing & visual inspection Justification: Code compliance is very difficult in existing construction. Testing seems to meet the intent. 4 Subcommittee: Residential Weatherization and Ventilation Specifications

  8. Option C Modifications to ASHRAE 62.2 Equation 6 5 1 Subcommittee on Residential Weatherization and Ventilation Specifications

  9. Ventilation System Approach: Option C Rational • Standard 62.2 is not a IAQ standard. It is an air flow standard. • Evidence of its impact on IAQ is circumstantial. • High level of ventilation does not guarantee good IAQ . • Low levels do not insure bad IAQ. • Increased air flow certainly leads to more space conditioning. • Spot ventilation fans directly address pollution sources. • Specific measures to encourage this part of the system. • Reduce the total target for air flow • Reduce the threshold for which ventilation systems are required Subcommittee on Residential Weatherization and Ventilation Specifications

  10. Option C Modifications to ASHRAE 62.2 Equation • Equation changed: vent requirement related to house size reduced by 25% (from .01 to .0075 cfm/sqft) • Justification: • More consistent with current thresholds in regional ventilation specifications. Results in a target tightness of about 10 ACH50 before whole house ventilation systems (as compared to 9 ACH50 in current RTF standard). • Shifts the focus of the standard away from house volume and toward occupancy. Ventilation is mostly for the people in the houses, not for the houses themselves. • The overall relationship between ventilation fan flow and IAQ is weak. Source strength dominates until overall ventilation rates fall below .25 ACH. (Offermann, 2009) • Increased tightness threshold about 2 ACH50 before a whole house fan is required results in energy savings. 5 Subcommittee on Residential Weatherization and Ventilation Specifications

  11. Option C Modifications to ASHRAE 62.2 Equation 6 • Equation changed: Full credit for air tightness measurements using a blower door instead of assigning default credit for tightness • Justification: • The 62.2 Standard is arbitrary and has the effect of increasing the ventilation target even when the structure is very leaky. Has the effect of demanding incrementalventilation at high leakage rates • 62.2 has no justification for the increased rate (over 62-89 or over the existing RTF standard) in IAQ studies. • Tightness test required in this proposed standard so no default flow (as specified in 62.2) is required. Subcommittee: Residential Weatherization and Ventilation Specifications

  12. Option C compared to 62.2An Example House • House Description: 1650 ft2, single story, 3 bedrooms, 2 baths, 4 occupants, Seattle • Tightness Level: 7.3 ACH50 (let’s assume house has received air sealing measure) Subcommittee: Residential Weatherization and Ventilation Specifications

  13. Subcommittee on Residential Weatherization and Ventilation Specifications

  14. Examples: Pre and post ACH 69 homes Subcommittee: Residential Weatherization and Ventilation Specifications

  15. Using the Ventilation calculator (equation-modified ASHRAE Std. 62.2), determine the whole-house continuous ventilation rate with the following inputs: Post- air sealing air changes per hour Spot ventilation: either default flow for operable fans, tested fan flow, or rated fan flow (using ASHRAE 62.2 prescriptive standard) Installed whole-house ventilation may be a replacement spot ventilator, designated whole-house fan or HRV/ERV, or as approved to meet calculated flow. For next three years, the ventilation standard will only apply to “air-sealing as a measure.” Other weatherization measures will be studied for their ventilation impacts on houses. Proposed RTF Ventilation Standard Subcommittee: Residential Weatherization and Ventilation Specifications

  16. Over the next three years… Seek more data on house tightening approaches, especially from prescriptive WX measures. Seek more data on actual ventilation system operation, flow and occupant use. Monitor ASHRAE discussions, revisions and updates. In three years… Update specifications. Next Steps Subcommittee: Residential Weatherization and Ventilation Specifications

  17. The subcommittee needs RTF approval for direction on the ventilation specifications in order to finalize revisions to the weatherization specifications. The subcommittee recommends using the proposed modifications (Option C) to ASHRAE 62.2 to develop the ventilation specifications. RTF Decision Subcommittee: Residential Weatherization and Ventilation Specifications

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