HVAC Sizing: Flaws and Fudging

Transcription

1 This webinar is being recorded and will be available at: HVAC Sizing: Flaws and Fudging

2 Introduction Presented by: Mike Turns, Senior Program Manager Performance Systems Development (PSD) Principle Investigator, Pennsylvania Energy Code Field Study/Penn Energy Codes Program

3 Continuing Education PA L&I CEUs for code officials for this webinar ($20 admin fee): After the webinar, go to: Answer all poll questions Enter the code to be given later in the webinar Groups watching the webinar from the same computer must send a signin list including the name, and signature of each attendee. These individuals must also take and pass the post-webinar quiz. 4

4 Overview Review of 3 main field study findings HVAC Sizing Benefits and Consequences ACCA design process overview How to review a Manual J Manual S oversizing limits Incorporating into your process Review of 3 main field study finds and PEC offerings 5

5 QUICK FIELD STUDY REVIEW 6

6 Count High-Efficacy Lamps (%) % All Homes No. % 50% HE 39 62% <50% HE 24 38% HighEffLamps%

7 Insulation Installation Quality Over half of installations were Grade II or Grade III GreenBuildingAdvisor.com 8

8 CFM25 Count Field Study Results Total Leakage (CFM25/100 sq. ft.) 6 12 CFM All Climates Count 52 No. > Percent > 12 44% Average 19 Median 13 Max 69 Min CFM25/100 sq. ft.

9 What is your profession? POLL 1

10 Are there multiple people watching from your computer? If so, how many? POLL 2 11

11 Benefits and Consequences HVAC SIZING 12

12 ACCA Design Process ACCA has developed an entire HVAC system design process Code references Manuals J, S, and D 13

13 Who Is ACCA? ACCA (Air Conditioning Contractors of America) is the association of HVAC (heating, ventilation, air conditioning, building performance) contractors. They write the standards for the design, maintenance, installation, testing, and performance of indoor environment systems. Provide contractor accreditation (ACCA Quality Assured Contractors) Software powered by ACCA 14

14 Equipment Sizing Code References IECC 403.6: Heating and cooling equipment shall be sized in accordance with Section M of the International Residential Code. HVAC systems shall be sized in accordance with Manual S based on loads calculated using Manual J 15

15 Rules of Thumb vs. Calculations Rules of thumb XXX sqft per ton, or XXX CFM per ton Will this work for a house Built in 1970? 2016? Code? ENERGY STAR? Zero Energy Ready? Passive House? 15% window-to-wall ratio? 25%? Facing west? Facing south? With air leakage 3 ACH50? 7ACH50? With leaky ducts in an attic? Tight ducts 100% inside? 16

16 Why Size Correctly? Under-sizing (rare) leads to: Hot or cold occupants Oversizing leads to: Higher installed costs bigger equipment/ducts Lower equipment efficiency Poor humidity control/potential for mold growth Occupant discomfort Large temperature swings Temperature variation throughout house Premature equipment failure/service calls 17

17 DOCUMENTATION 18

18 ACCA Resources Brochures for code officials and contractors 19

19 20 Software Reports

20 Design Temperatures Design temperatures Indoor design temp. per code: 72 heating, 75 cooling (IECC 302.1) Outdoor design temp (Manual J Table 1) + location 21

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22 Windows and Glass Doors Do U-factors/SHGCs match the plans/code? Are the areas reasonable and do they match plans? Roof overhang adjustments House orientation (N,S, E, W) 23

23 Insulation and Infiltration Above grade walls, below grade walls, ceilings, floors Do the R-values meet code and match the plans? Are the areas reasonable? Infiltration Infiltration rate (tight, semi-tight, average, semi-loose, loose) Code home should be tight, semi-tight or average Tested value is even better (based on experience) Above grade volume (L x W x H) 24

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26 Editable Air Leakage Verification Form Download editable blower door and duct leakage testing forms at: /resources/pa-energy-codetoolkit/ 27

27 Internal Heat Loads Appliances Kitchen appliances entered (1,200 to 2,400 Btu/h) Number of occupants # bedrooms + 1 Each person = 230 Btu/h sensible / 200 Btu/h latent 28

28 Ducts Duct location Conditioned vs. unconditioned space Unconditioned spaces = attics, crawls, basements, etc. Duct insulation Correct R-values? Duct leakage Average sealed, notably sealed, extremely sealed Tested value is better (based on experience) 29

29 Editable Air Leakage Verification Form Download editable blower door and duct leakage testing forms at: /resources/pa-energy-codetoolkit/ 30

30 Ventilation Spot ventilation Exclude intermittent kitchen and bath fans Whole-house ventilation Include flow rates (cfm) Heat recovery ventilation Recovery efficiency 31

31 Training and Credentials ACCA QA Accreditation RSES Certified HERS Raters Certified BPI Building Analysts and Envelope Professionals Duct and Envelope Testing (DET) Verification Technicians 32

32 Which of the following items is the LEAST important contributor to heating and cooling loads? Infiltration Duct Location and Leakage Opaque doors Window area and orientation POLL 3 - QUIZ 33

33 Equipment Selection Manual S is equipment selection Use loads calculated from Manual J 34

34 Manual S Verification Heating equipment output 140% of calculated heat loss (or next nominal size) Cooling equipment output 115% of calculated heat gain (or next nominal size) Heat pumps may be up to 125% oversized Design air flow Actual equipment rated air flow (cfm) on medium speed +/- 15% of design air flow 35

35 Heating Equipment Selection - Example Manual J calculated heat loss = 50,918 Btu/h Actual selected furnace output = 52,000 Bth/h Oversize limit is 140% of 50,918 or 1.4 x 50,918 = 71,285 Btu/h OK Selected furnace (52,000 Btu/h) < oversize limit (71,285 Btu/h) 36

36 Cooling Equipment Selection - Example Manual J calculated heat gain = 27,543 Btu/h Actual selected AC output = 30,000 Bth/h Oversize limit is 115% of 27,543 or 1.15 x 27,543 = 31,674 Btu/h OK Selected furnace (30,000 Btu/h) < oversize limit (31,674 Btu/h) 37

37 Cooling Equipment Selection - Example Design air flow from Manual J = 1,116 cfm Selected blower cfm on medium speed = 1,000 cfm Acceptable air flow range = +/- 15% of 1,116 cfm 0.15 x 1,116 = 167 cfm Acceptable range = 949 to 1,283 cfm Selected blower cfm is within this range 38

38 SUMMARY 40

39 Summary Ask for ACCA design documentation from the permit applicant (code officials) or the HVAC contractor (builders) Ensure documentation reflects the home design Design temperatures Window areas and orientation Insulation R-values and component areas Infiltration and ventilation Duct location and leakage Internal gains Oversizing limits Heating = 1.4X design heat loss Cooling = 1.15X design heat gain (1.25 for heat pumps) Blower cfm = +/- 15% of design air flow 41

40 General Focus Areas Duct leakage High-efficacy lighting Insulation installation quality Resources at pennenergycodes.com

41 Next Month s Webinar Insulation Installation July 26, 2016 Noon to 1:00 pm PennEnergyCodes.com/events 43

42 Continuing Education Hours You will receive a follow-up in about an hour Follow the link and enter: PEH45 Or, do it now: