Residential Weatherization and Ventilation Subcommittee

Ventilation Specification Proposed

June 1, 2011

Residential Weatherization and Ventilation Subcommittee

Ventilation Specification Proposed

June 1, 2011

Subcommittee: Residential Weatherization and Ventilation1

Subcommittee Lessons Learned

Subcommittee: Residential Weatherization and Ventilation Specifications 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.

Deciding on a Ventilation Standard: Guiding Factors

Subcommittee: Residential Weatherization and Ventilation Specifications 3

1. Measures should not cause harm.

2. Base the standard on ASHRAE 62.2.

3. Avoid ventilation standards that preclude energy savings from air tightness measures.

4. Be mindful of cost; the recommended path should be “doable” in utility WX programs.

5. 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.

6. Recognize interaction of spot ventilation and how it can contribute to overall ventilation as well as address IAQ in source locations.

ASHRAE 62.2 – Whole-House Ventilation Requirements(Existing Houses with blower door test results)

Subcommittee on Residential Weatherization and Ventilation

Specifications4

Standard Ventilation Rate(Section 4.1)

Infiltration Credit(Section 4.1.3)

Local Exhaust Adjustment(Section A3)

Based on ASHRAE 62.2

Subcommittee: 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.

Subcommittee Vote and Results

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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 VotesB: 4 VotesC: 15 Votes

Modifications to ASHRAE 62.2(proposed in all options)

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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

3

4

Max ventilation rate: Installed equipment cannot exceed 150% of the prescribed rate.

Justification: Avoid wasting energy by over-ventilating.

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.

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.

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Subcommittee on Residential Weatherization and Ventilation

Specifications8

Option C Modifications to ASHRAE 62.2 Equation

5 6

1

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

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Option C Modifications to ASHRAE 62.2 Equation

Subcommittee on Residential Weatherization and Ventilation

Specifications10

5 Equation changed: vent requirement related to house size reduced by 25% (from .01 to .0075 cfm/sqft)

Justification: 1.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).2.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.3.The overall relationship between ventilation fan flow and IAQ is weak. Source strength dominates until overall ventilation rates fall below .25 ACH. (Offermann, 2009) 4.Increased tightness threshold about 2 ACH50 before a whole house fan is required results in energy savings.

Option C Modifications to ASHRAE 62.2 Equation

Subcommittee: Residential Weatherization and Ventilation Specifications 11

Equation changed: Full credit for air tightness measurements using a blower door instead of assigning default credit for tightness

Justification: 1.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 incremental ventilation at high leakage rates2.62.2 has no justification for the increased rate (over 62-89 or over the existing RTF standard) in IAQ studies. 3.Tightness test required in this proposed standard so no default flow (as specified in 62.2) is required.

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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 12

ID Kitchen Bath 1 Bath 2

Minimum Whole-House

Ventilation Requirement

Estimated Cost

Whole-House Ventilation

Requirement

Estimated Cost

a 100 cfm, tested 50 cfm, tested 50 cfm, tested 24 cfm $100 none $0b 100 cfm, tested 50 cfm, tested non-existant 36 cfm $100 none $0c 50 cfm, tested 25 cfm, tested 25 cfm, tested 49 cfm $100 28 to 42 cfm $100d non-existent 50 cfm, tested non-existent 61 cfm $600 41 to 62 cfm $100e non-existent 61 cfm, tested non-existent 61 cfm $100 41 to 62 cfm $100f 100 cfm, tested non-existant non-existent 49 cfm $100 28 to 42 cfm $100g operable, untested operable, untested operable, untested 74 cfm $600 28 to 42 cfm $100 or $600h non-existent non-existent non-existent 74 cfm $600 53 to 80 cfm $600

62.2 Option CSpot Fan Condition Scenario

Subcommittee on Residential Weatherization and Ventilation

Specifications13

0

10

20

30

40

50

60

70

80

90

100

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Requ

ired

Who

le H

ouse

Con

tinu

ous V

entil

ation

(cfm

)

House Leakiness (ACH 50)

Whole House Ventilation Rate Comparison: Option C vs 62.2(1650 ft2 single-story house in Seattle with 2 bathrooms, 3 bedrooms, and 4 occupants)

Option C - All Spot Fans

62.2 - All Spot Fans

Option C - Half Spot Fans

62.2 - Half Spot Fans

Option C - No Spot Fans

62.2 - No Spot Fans

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Examples: Pre and post ACH 69 homes

Proposed RTF Ventilation Standard

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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.

Next Steps

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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.

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

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