Residential HVAC Load Sizing Training October 14, David Kaiser Green Code Plan Reviewer

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1 Residential HVAC Load Sizing Training October 14, 2015 David Kaiser Green Code Plan Reviewer

2 DCRA - Green Building Division Regulations of green codes including: Green Building Act Green Construction Code Energy Conservation Code Operates within the structure of DCRA s permitting and inspections groups, with work including reviews of construction documents, conducting building inspections, and collaborating with the community to further the efforts to build a more sustainable DC.

3 Training Objectives Identify why HVAC load sizing is important. Understand the basic science of load sizing Identify the EVS measure that is satisfied with load sizing. Recognize the exemptions to load sizing. Identify documentation and details necessary to comply. Determine how to size HVAC systems to the Manual J outputs.

4 Navigating EVS

5 IECC R403.6: Equipment sizing (Mandatory) Requires heating and cooling equipment sizing in accordance with ACCA Manual S-10, Residential Equipment Selection. ACCA Manual J-11, Residential Load Calculations, 8 th edition.

6 Heating/Cooling System Sizing Why it matters Provide comfort & humidity control Reduce the possibility of indoor mold and mildew. Translate to smaller equipment. Optimize installed cost. Reduce operating cost. Improve reliability. Reduce airflow noise both internal and external. Minimize service loads imposed on utility grids. Keep utility cost more constant

7 What Affects your Load: Understand the Basic Science of Load Sizing Primary Summer Loads Windows Internal Loads: Lighting, Oven, Dryer, Dishwasher Other Exterior Walls I.e a Pizza Making party at 4PM on a hot day of the year.

8 Understand the Basic Science of Load Sizing What Affects your Load: Primary Winter Loads Heat Loss Through Exterior Walls Via Conduction Outside air into your home (Ventilation, Infiltration) I.e. Middle of the night with no lights, equipment going on very cold day.

9 Temperature Understand the Basic Science of Load Sizing Max Temp Time Min Temp Heat (Btus) # HVAC Cycles = 9 Time Over-Sized System

10 Understand the Basic Science of Load Sizing Temperature Max Temp Time Min Temp Btus # HVAC Cycles = 6 Time Manual J Right-Sized System

11 DCRA Exemptions to Load Sizing A replacement in kind of an existing system When extending ductwork from an existing system into an addition When HVAC system is 1.5 tons or less HVAC system has multiple stages of cooling or is variable refrigerant flow

12 Temperature Understand the Basic Science of Load Sizing Max Temp Time Min Temp Btus # HVAC Cycles = 4 Time Dual Speed Compressor System

13 Understand the Basic Science of Load Sizing Temperature Max Temp Time Min Temp Btus # HVAC Cycles = 1 Time Variable Refrigerant Volume System

14 So you want to use Manual J... Now What?

15 5 Steps to Manual J Compliance Step 1: Use Approved Software Step 2: Define Building Thermal Envelope Areas Step 3: Select Values of Components Step 4: Fill In DC & Project Specific Inputs Step 5: Select HVAC System

16 Step 1: Use Approved Software

17 Manual J Step 2: Define Building Thermal Envelope The "Building Thermal Envelope" represents the boundary that separates conditioned space from unconditioned space or the outdoors.

18 Manual J Step 2: Define Building Thermal Envelope

19 Manual J Step 2: Define Building Thermal Envelope

20 Manual J Step 2: Define Building Thermal Envelope

21 Manual J Step 2: Define Building Thermal Envelope Where is the Thermal Boundary for bottom unit? How Many Systems do we need? Where is the Thermal Boundary for top unit?

22 Manual J Step 2: Define Building Thermal Envelope Where is the Thermal Boundary for bottom unit? Where is the Thermal Boundary for top unit?

23 Step 2: Elements of the Thermal Envelope A building thermal envelope includes all components of a building that enclose conditioned space: Roof Walls Floor Doors Windows

24 Manual J Step 3: Select Values of Components For new construction assemblies:

25 Manual J Step 3: Select Values of Components For existing construction components: - Use the current assembly value Used during level 3 alterations and additions when a portion of the building is being left alone but a new HVAC system is being added.

26 Step 3: Manual J Inputs, Select Values of Components conditioned floor area window area ceiling area building orientation wall construction insulation values window construction or U-value window solar heat gain coefficients (SHGC)

27 Step 4: Fill In DC & Project Specific Inputs Summer exterior Temperature = 91 Summer interior Temperature = 75 Winter exterior Temperature = 17 Winter interior Temperature = 70 number of occupants living in the home = # of bedrooms + 1 estimated or measured building air-leakage values (infiltration) - If software gives option choose average or equivalent between 5 and 7 ACH50, (between 0.25 and 0.35 natural ACH) mechanical ventilation = amount required by IMC summary of lighting and appliances Sensible Heat Ratio (SHR) = between 0.70 and 0.75

28 Example of Manual J Input Report

29 Example of Manual J Output Report

30 Step 5: Select HVAC System

31 Example of Manual J Output Report

32 Step 5: Select HVAC System Heating Load 65,774 x 1.4 = 92,083 Max output Btu 100,000 BTU rated furnace puts out 80,000 BTUs at 80AFUE

33 Example of Manual J Output Report 26,

34 Step 5: Select HVAC System Heating Load 30,923 x 1.15 = 35,561 Max output Btus 36,000 BTU rated AC Total Cooling 30,000 BTU rated Sensible Load

35 DCRA Necessary Details - Outputs Component Summary (Areas, Uvalues, SHGCs) Project Summary Mechanical Schedule Model numbers of compressor AHU BTUs of Heating and Cooling Compressor Stages if applicable Efficiency

36 Step 5: Select HVAC System

37 Questions?