Humidity Control: Tales From the Damp Side Michael Brown, ICF Frank Swol, EAM Associates February 25th, 2020 ICF proprietary and confidential. Do not copy, distribute, or disclose. 1
Agenda ▪ Humidity Introduction ▪ Suggestions and Best Practices ▪ Humidity Models ICF proprietary and confidential. Do not copy, distribute, or disclose. 2
Humidity Introduction ICF proprietary and confidential. Do not copy, distribute, or disclose. 3
Humidity Basics ▪ Air Contains Water ▪ We measure with relative humidity (0-100%) ▪ Hot air can hold more water than cold air ▪ When you cool air down it loses water (condensation) Example ▪ Maine is cold! ▪ … and humid?! ICF proprietary and confidential. Do not copy, distribute, or disclose. 4
Humidity Basics Example Specific volume (m³/kg) Absolute humidity (kg/kg) Relative humidity (%) 100 90 80 70 60 50 40 0.0550 190 Outdoors Indoors Humid 30 0.0500 105 180 Dry Bulb Temp (F) -6 °F 67 °F 67 °F 0.0450 170 Relative Humidity (%) 98 % 24 % 100 % 100 160 0.0400 1.020 150 Absolute Humidity (kg/kg) 0.0006 0.0033 0.0142 95 0.0350 140 Cups of Water 20 130 1 4 18 90 0.0300 in my House 120 1.000 110 85 0.0250 100 80 0.0200 90 75 80 10 70 0.0150 0.980 70 65 60 60 0.0100 50 55 50 40 45 0.0050 30 40 P2 Density (kg/m³) Density (kg/m³) Density (kg/m³) Density (kg/m³) Density (kg/m³) 35 20 30 Wet bulb temperature (°F) 25 10 0.960 Enthalpy (kJ/kg) 20 1.300 1.250 1.200 1.150 1.100 1.050 P1 0 15 10 0.760 0.780 0.800 0.820 0.840 0.860 0.880 0.900 0.920 0.940 0.0000 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 Dry bulb temperature (°F) Dry bulb temperature Absolute humidity Relative humidity Enthalpy Wet bulb temperature Specific volume Density ICF proprietary and confidential. Do not copy, distribute, or disclose. 5
Balancing Act: Moisture In – Moisture Out = Humidity Moisture In: Moisture Out: • Infiltration • Air Conditioner • WH Ventilation • Local Ventilation • Cooking • Bathing • Drying Bldg. Materials ICF proprietary and confidential. Do not copy, distribute, or disclose. 6
Why Do We Care About High Humidity? ▪ It’s uncomfortable! ▪ Excess moisture can lead to mold and other biological pollutants ▪ Health concerns (e.g., asthma, allergies) ▪ Building material decay ▪ Recommended < 60% RH Mold ICF proprietary and confidential. Do not copy, distribute, or disclose. 7
Efficient Homes & Humidity Control ▪ Efficient homes tend to decrease sensible load, but not latent load as much ▪ True with modern Code, HERS Rated, and ENERGY STAR homes! ▪ With relatively high latent loads, more likely to meet setpoint quickly, short cycle, and not dehumidify Sensible Load (temperature) Latent Load (moisture) Home Efficiency ICF proprietary and confidential. Do not copy, distribute, or disclose. 8
Equipment sizing and dehumidification ▪ Water condenses and drains away Right-Sized ▪ Takes time AC ▪ Not enough time ▪ ‘Short cycles’ Oversized ▪ Cools but doesn’t AC dehumidify ICF proprietary and confidential. Do not copy, distribute, or disclose. 9
Suggestions / Best Practices ICF proprietary and confidential. Do not copy, distribute, or disclose. 10
Humidity Control Research Low / No-Cost Solutions ▪ Mid-Atlantic builders in an ICF new homes EE program were having trouble with high humidity. ▪ Wanted to know about ventilation, and options before an expensive dehumidification system. ▪ Recommendations summarized in a white paper. ▪ Make sure you do these recommendations right before jumping to supplemental dehumidification. ICF proprietary and confidential. Do not copy, distribute, or disclose. 11
HVAC Solutions: Sizing ▪ ENERGY STAR HVAC Design Report & Rater Design Review Checklist ▪ Calculate accurate loads ▪ Use industry standard practices ▪ Ensure design = actual home ▪ Properly size equipment ▪ Enough sensible and latent capacity ▪ Limit oversizing! ICF proprietary and confidential. Do not copy, distribute, or disclose. 12
HVAC Solutions: Commissioning ▪ ENERGY STAR HVAC Commissioning Checklist ▪ Commission system to ensure equipment operates as designed ▪ Duct leakage ▪ Airflow ▪ Refrigerant Charge ICF proprietary and confidential. Do not copy, distribute, or disclose. 13
HVAC Solutions: Sensible Heat Ratio (SHR) 14 SEER 16 SEER ▪ Lower SHR = more latent capacity Nominal Capacity (Tons) 3.0 3.0 ▪ Pay attention to SHR when selecting equipment. SHR 0.75 0.82 Latent Capacity (kBtuh) 9.0 6.5 ▪ SHR and latent capacity change with conditions, consider evaluating off peak conditions. 0.86 12 0.84 10 0.82 Latent Capacity 8 0.8 SHR 0.78 6 0.76 4 0.74 2 0.72 0.7 0 70 75 80 85 90 95 100 105 110 70 75 80 85 90 95 100 105 110 Outdoor Temperature Outdoor Temperature ICF proprietary and confidential. Do not copy, distribute, or disclose. 14
HVAC Solutions: Supply Fan Overrun ▪ Supply fan overrun: HVAC fan runs for a short period after compressor turns off ▪ Provides a little extra cooling ▪ Increases SEER rating ▪ Adds moisture back to the living space. ▪ Disable supply fan overrun if you struggle with humidity control. ▪ 90 second fan overrun in Miami leads to 1,300 additional hours (53 days!) above 60% RH http://publications.energyresearch.ucf.edu/wp-content/uploads/2018/06/FSEC-PF-443-08.pdf ICF proprietary and confidential. Do not copy, distribute, or disclose. http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1716-07.pdf 15
Ventilation Solutions: Local Mechanical Exhaust ▪ ENERGY STAR Rater Field Checklist ▪ Besides AC local exhaust is main way to remove moisture directly from the source ▪ Make sure to: ▪ Measure airflow rate ▪ Verify meets minimum rates 55 CFM ▪ Verify exhausts directly outdoors Outdoors ICF proprietary and confidential. Do not copy, distribute, or disclose. 16
Ventilation Solutions: Recommended Mechanical Ventilation Strategies Balanced Exhaust Supply (ERV) Hours Modeled hours above 60% RH ICF proprietary and confidential. Do not copy, distribute, or disclose. https://www.nrel.gov/docs/fy14osti/60675.pdf 17
Homeowner Education Solutions ▪ Educate homeowners on how their actions can impact humidity control: ▪ Use kitchen and bathroom ventilation, or use ventilation with humidistat controls ▪ A higher cooling setpoint will mean less dehumidification ▪ Set fan mode to “AUTO” not “ON” FAN ON AUTO ICF proprietary and confidential. Do not copy, distribute, or disclose. 18
Humidity Models ICF proprietary and confidential. Do not copy, distribute, or disclose. 19
When is there high humidity? 400 Month 200 (hours > 60% RH) 0 J F M A M J J A S O N D 60 Outdoor Temp. (hours > 60% RH) 30 0 40 45 50 55 60 65 70 75 80 85 90 95 100 ENERGY STAR v3.1 home modeled in Baltimore MD using BEopt ICF proprietary and confidential. Do not copy, distribute, or disclose. 20
Measure Humidity Savings Humidity Reductions Humidity (hours > 60% RH) Bathroom WH Baseline HPWH AC SHR Total Impact Exhaust Ventilation • ENERGY STAR • Modeled 2x the • Heat pump water • Improving from 0.82 • Improving from • 66% reduction v3.1 in MD shower load heater in to 0.73 sensible Exhaust to ERV (27 days) • 964 hours (40 days) • Minimal total space • Large impact • Not cumulative due conditioned space heat ratio • Likely challenges humidity > 60% RH impact, localized to interactive effects impact architecturally ENERGY STAR v3.1 home modeled in Baltimore MD using BEopt ICF proprietary and confidential. Do not copy, distribute, or disclose. 21
Ventilation Strategies Balanced Balanced Supply Exhaust (HRV) (ERV) $1,874 Energy $1,818 $1,817 $1,813 Cost 964 889 724 Humidity 444 (hours > 60% RH) ENERGY STAR v3.1 home modeled in Baltimore MD using BEopt ICF proprietary and confidential. Do not copy, distribute, or disclose. 22
Investing in Efficiency / Humidity Tankless Window 16 SEER Baseline ERV DHW Upgrade AC 69 68 68 ERI 62 62 $2,544 Incremental $1,284 Measure $902 $247 Cost $- 603 591 571 522 Humidity 246 (hours > 60% RH) ~2012 IECC home modeled in Baltimore MD using BEopt ICF proprietary and confidential. Do not copy, distribute, or disclose. 23
Key Takeaway ▪ Consider humidity control when improving home efficiency ~2012 IECC home modeled in Baltimore MD using BEopt ICF proprietary and confidential. Do not copy, distribute, or disclose. 24
Case Study: Multi-Family Project
3-Story Low-Rise MF Building in Delaware Climate Zone 4 ( ~4 miles from coast) • 2012 IECC construction • Summer 2018 • Various units were experiencing high indoor • relative humidity ( >70%) and mold growth Mold located at door frames, walls, and on • absorbent materials (clothes, furniture, knickknacks) Field inspection and analysis determined a • series of fundamental design, product selection, and installation errors to be the causal factors
3-Story Low-Rise MF Building in Delaware Two disclaimers before we • continue: – NOT a HERS Rated or Energy Star project! – NOT designed or constructed with Rater’s involvement !
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