FUNDAMENTALS of ASHRAE 62.2 2007 VENTILATION AND ACCEPTABLE INDOOR AIR QUALITY IN LOW-RISE RESIDENTIAL BUILDINGS by Joe Kirkpatrick Deputy Building Official City of Irvine jkirkpatrick@ci.irvine.ca.us x 1 2 USEFUL RESOURCES: CEC hotline: (800) 772-3300 On the CEC Website @ http://www.energy.ca.gov/title24/2008standards/ There are links to: Indoor Ventilation Minimum Best Practices Guide, Based on ASHRAE 62.2 2008 Residential Compliance Manual Also, may purchase a copy of the standard from ASHRAE @ http://www.ashrae.org/ Applicability ASHRAE 62.2 is a reference standard of the 2008 California Building Energy Efficiency Standards (BEES) under: Sub-Chapter 7 Low-Rise Residential Buildings-Mandatory Features and Devices, Section 150-Mandatory Features 3 4 Item o of section 150 Review-Definitions Section 101 150(o) Ventilation for Indoor Air Quality. All dwelling units shall meet the requirements of ANSI/ASHRAE Standard 62.2.Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. Window operation is not a permissible method of providing the Whole Building Ventilation required in Section 4 of that Standard. Low-Rise Residential Building is a building, other than a hotel/motel that is of Occupancy Group R, Division 1, and is multi-family with three stories or less, or a single family residence of Occupancy Group R, Division 3, or an Occupancy Group U building located on a residential site. 5 6 1
Review- Section 100, item (e) 2. D says in part To comply with Title 24, Part 6 (i.e. BEES), newly constructed low-rise residential buildings must meet the requirements of: Mandatory measures: The applicable provisions of Sections 110 through 119, and 150; and Either: Performance approach: Section 151(a) through (e); or Prescriptive approach: Section 151(a) and (f). Review- Section 152, item (a) says in part Section 152(a) Additions. Additions to existing residential buildings shall meet the requirements of Sections 111 through 118, Section 119, and Section 150, and either Section 152(a)1 or 2. EXCEPTION 5 to Section 152(a): Additions 1,000 square feet or less are exempt from the requirements of Section150(o). For additions larger than 1,000 ft², application of Section 150(o) shall be based on the conditioned floor area of the entire dwelling unit, not just the addition. 7 8 To Summarize thus far: ASHRAE 62.2 applies to: All new low-rise residential bldgs. R occs. 3 stories or less and by applies it means the entire ASHRAE 62.2 Standard applies. To Summarize thus far: ASHRAE 62.2 applies to: All low-rise residential additions greater than 1,000 square feet. -whole building ventilation designed for the total square footage. All other requirements only apply to the extent that the addition or remodel puts the issue in play, e.g. a new bathroom would be required to meet the local exhaust requirements-note this is a practical interpretation confirmed by CEC. 9 10 ASHRAE 62.2 Any questions so far? What is ASHRAE 62.2 all about? Its purpose is to define roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality (IAQ) in low-rise residential buildings. 11 12 2
More About ASHRAE 62.2 ASHRAE 62.2 is an 18 page document and is best known for the Whole-Building Ventilation requirements. But there is a lot more ASHRAE 62.2 also requires: Local exhaust- including minimum ventilation for kitchens and bathrooms. Clothes dryer to be exhausted to the outdoors. Limitations on the total net exhaust flow to ensure against insufficient combustion and ventilation air. Measures to protect against pollutants originating in a garage from entering the home. Ventilation openings for habitable space. Minimum filtration standard. Air inlet standards. Sound ratings for fans. Fan Control requirements. Airflow Rating. 13 14 Local exhaust- minimum ventilation for kitchens and bathrooms. Section 5. Local Exhaust: Must be either intermittent or continuous mechanical exhaust: Intermittent 1) controls designed to be operated by the occupant as needed, i.e. switch control, 2) Ventilation rates per Table 5.1-Kitchen: 100 cfm, Bathroom: 50 cfm. Continuous 1) system must be designed to operate when the building is occupied and without occupant intervention but have readily accessible override controls, 2) Ventilation rates per Table 5.2-Kitchen: 5 air changes per hour, Bathroom: 20 cfm. Note: Continuous approach is somewhat complicated due to control requirements. Be sure designer/installer clearly defines approach before passing rough inspection. 15 16 17 18 3
Word of Caution Do no harm... Be sure any fan designated for continuous operation is listed for it. Fans not rated for continuous operation left on accidentally are a common cause of residential fires. Last thing we want to do is encourage continuous operation with a fan not designed for it. 19 20 Clothes dryer to be exhausted to the outdoors. Section 6.3 requires clothes dryers to be exhausted directly to the outdoors mechanical code says same thing, see 504.3 of CMC which says moisture exhaust ducts shall terminate on the outside of the building and shall be equipped with a back-draft damper. Limitations on The Total Net Exhaust Flow Section 6.4 Combustion and Solid-Fuel Burning Appliances. This section aims to ensure that fuel burning appliances are provided with adequate combustion and ventilation air Applies where atmospherically vented appliances are located inside the pressure envelope, for example a water heater or FAU located in a hall closet, provision does not apply if appliances are direct vented. Limits the exhaust rate of the two largest fans to 15cfm/100sf unless compensating outside air is provided. So must add two largest fan capacities together divide by square footage within the envelope and multiply by 100. If greater than 15 a compensating supply is required. 21 22 Garages Section 6.5 Garages. This section aims to protect habitable space adjoining a garage from pollutants originating in the garage from entering the habitable space. Intervening doors must be gasketed or made substantially airtight BEES already covers this, see section 116 (a) limits air leakage to 0.3 cfm/sf of door area. Where HVAC air handler or return ducts are located in the garage- total air leakage shall not exceed 6% of total fan flow at 0.1 inch water column. ASHRAE 62.2 Any questions so far? 23 24 4
Ventilation Openings for Habitable Space. Section 6.6 Ventilation Opening Area. This section defines minimum ventilation openings for habitable spaces. 4% of the floor area but not less than 5 sf, note section 1203.4.1 of the CBC and section R303 of the CRC also require the 4% minimum. Also refers to section 6.8 which requires that that operable windows be readily accessible to the occupants. Minimum Filtration Standards Section 6.7 Minimum Filtration. This section defines minimum Merv 6 filtration efficiency for mechanical systems that: 1) supply air through duct work exceeding 10 feet and 2) through a thermal conditioning component, e.g. typical HVAC system will have to be fitted with Merv 6 or better filters. 25 26 Air inlet standards: Section 6.8 Air inlets. This section requires a minimum 10 foot distance between air inlets and sources of contamination such as a stack, vent, exhaust hood, or vehicle exhaust. Sound Ratings For Fans. Section 7.2 Sound Rating For Fans. This section defines minimum sound ratings for fans: Continuous fans < 1 sone. Note: Section R303.4.1 of the CRC has same requirements, and the CMC limits exhaust terminations in a similar way. 27 Intermittent fans < 3 sones. Note: air handlers and remote mounted fans, i.e. not in the habitable space and having at least 4 feet of intervening duct to the grill are exempt from this requirement. 28 Airflow Rating. Section 7.3 Airflow Rating. This section identifies delivered airflow testing protocols or the more practical and typically utilized alternative of using airflow ratings of specified fans at 0.25 inch water column provided ducting follows prescriptive duct sizing requirements of Table 7.1. Section 4 of ASHRAE 62.2: Requires a mechanical exhaust system, supply system or combination system. Requires a minimum ventilation rate calculated using equation 4.1a, or taken from a Table 4.1a. Specifies control standards. Allows for continuous or intermittent operations. 29 30 5
Whole house ventilation may be provided by single or multiple fans. And these fans may double as required local exhaust fans for a kitchen and bathroom. Design decisions/ramifications: 1. Use of exhaust only, supply only, or combination-how this is done determines overall system design. 2. Use of continuous operated fan or intermittentintermittent design requires potentially significant increase of fan flow rate, see section 4.4 of the standard, also increases likelihood that total net exhaust flow exceeds standard limits, see section 6.4 of the standard. Also, intermittent fans require automated controls. Minimum Ventilation rate: Equation 4.1a (from ASHRAE 62.2): Qfan = 0.01xAfloor + 7.5x(Nbr + 1) Where: Afloor = conditioned floor area, ft² Nbr = number of bedrooms; not to be less than one Qfan = ventilation airflow requirement = minimum fan airflow rating, (cfm) Note: As an option a value may be taken from Table 4.1a of the standard which will equal or exceed the calculated value. 31 32 The value calculated by equation 4.1a is the minimum and is only valid for continuous operation designation. If the fan is intended for intermittent operation two factors must be applied to this value which increase the design fan flow. Intermittent fan flow rate- Equation 4.2 (modified from ASHRAE 62.2): Qf = Qr / (εf) Where: Qr = ventilation air requirement from Eq. 4.1a (above), f = daily fractional on-time, e.g. 8hrs/day = 8/24 = 0.33 ε = ventilation effectiveness, (from Table 4.2), ranges from.33 1.0 Qf = fan flow rate during the on-cycle (cfm) 33 34 Intermittent fan flow rate- continued. Table 4.2 Table 4.2 Ventilation Effectiveness for Intermittent Fans Whole-Building Ventilation Rate Summary Daily Fractional On-Time, f f 35% 0.33 35% f < 60% 0.50 60% f < 80% 0.75 80% f 1.0 Fan runs at least once every 1.0 three hours Ventilation effectiveness, ε Intermittent fan flow rate- continued. So as we can see if the design value for continuous operation is divided by numbers less than one, the Qf is greater. For example say Q calculated using equation 4.1a is 60 cfms and the designer wishes to operate the fan for 10 hrs a day. Remember Qf = Qr / (εf) Qr = 60 cfm, f = 0.42 i.e. 10/24, ε = 0.50 (from Table 4.2, see previous slide) Qf = 60/[(.42) x (.5)] = 285 cfms 35 36 6
Intermittent fan flow rate- continued. Conclusion- the trade off for using an intermittent design is to increase the fan flow rate from 60 cfm to 285 cfm. In other words the initial construction cost is greater and this high volume fan may create other design impacts as well. Therefore likely not to be a common approach. Likely scenario: Consider a 2000 sf, three bedroom two bath home. Equation 4.1a (from ASHRAE 62.2): Qfan = 0.01xAfloor + 7.5x(Nbr + 1) = 0.01 x 2000 + 7.5x(3+1) = 50 cfm Also we know the minimum fan for a bathroom is 50 cfm and the minimum for the kitchen is 100 cfm assuming switch controlled intermittent operation is used as is usually the case. 37 38 2000 sf, three bedroom two bath home example continued Based on the calculation on the previous slide and in consideration of the minimum fan capacity for a bathroom, a logical and economical design choice is to specify one of the bathroom fans as the Whole Building Ventilation fan. What else? (1) To avoid increasing the capacity, must be designated as continuous. (2) If continuous must have a sound rating of 1 sone or less. (3) But may be switch controlled if appropriately labeled. 2000 sf, three bedroom two bath home example continued CEC considers the following appropriately labeled. This is an excerpt from their Best Practices Guide. To maintain minimum levels of outside air ventilation required for good health, the fan control should be on at all times the building is occupied, unless there is severe outdoor air contamination. 39 40 Is there anything else? Yes, the example illustrated represents the most common option. Why? It is fairly simple and straight forward. The most ELEGANT but costly solution, and thus the least likely to be encountered is a Balanced Design. Balanced Design What s a Balanced design you say? 41 42 7
Balanced Design A balanced design is ventilation system that balances supply/exhaust air inflow/outflow thus preventing pressurization or depressurization. Exhaust is either taken from a central location or ducted from locations likely to produce higher levels of contaminants, e.g. a kitchen, or family room, with the fresh (supply) air being dispersed throughout the home. Balanced Design Other considerations of Balanced design: Because of the expense, will only see such systems in high-end homes or homes having significant conditioning loads, i.e. expensive systems of which the premium for the balance system is a lesser overall percentage. To improve efficiency a balanced system might use exhaust air to heat or cool incoming air. For balanced designs, recommend requiring a design be done by a qualified HVAC contractor or mechanical engineer prior to permits. 43 44 ASHRAE 62.2 Any questions so far? Ashrae 62.2 Summary More than Just Whole Building Ventilation Whole Building Ventilation. Local exhaust- including minimum ventilation for kitchens and bathrooms. Clothes dryer to be exhausted to the outdoors. Limitations on the total net exhaust flow to ensure against insufficient combustion and ventilation air. Measures to protect against pollutants originating in a garage from entering the home. Ventilation openings for habitable space. Minimum filtration standard. Air inlet standards. Sound ratings for fans. Fan Control requirements. Airflow Rating. 45 46 Considerations: The requirements are by reference from the Energy Code (BEES) and many designers don t even have a copy of ASHRAE 62.2. Majority of jurisdictions do not perform a mechanical plan check on typical SFDs and duplexes. CF-1R does not cover any of the aforementioned requirements. What? But isn t it an energy code requirement? Req s are listed on the Mandatory Measures Summary MF-1R which references the code section without any specifics. What else to consider? CF-6R-MECH-05 requires the certification of installation to the aforementioned requirements. But for the most part only has check boxes adjacent to code sections. Given the multiple possibly inter-related requirements an integrated approach is recommended. 47 48 8
One possibility- Use Of Standard Interactive Notes that are completed by the designer and incorporated into the approved plans. Benefits of this approach: 1) Clear indication to designer of what is required; One possibility- Use Of Standard Interactive Notes. Benefits of this approach: 2) Provides for a coordinated, integrated, definitive approach; 49 50 One possibility- Use Of Standard Interactive Notes. Benefits of this approach: 3) facilitates understanding in the field inspectors may be thoroughly trained on the requirements, and may pass on understanding to the contractor who for the most part looks to the inspector to explain the code. One possibility- Use Of Standard Interactive Notes. Benefits of this approach: In summary-provides an EFFICIENT, TRANSPARENT way to be EFFECTIVE! Which of course is what we all want. 51 52 http://www.cityofirvine.org/civica/fileba nk/blobdload.asp?blobid=16568 & http://www.cityofirvine.org/civica/fileba nk/blobdload.asp?blobid=16569 Q & A Contact Information: Joe Kirkpatrick, Deputy Building Official, City of Irvine, (949) 724-6320 jkirkpatrick@ci.irvine.ca.us 53 54 9