Heating, Cooling, and Ventilation Strategies in Passive House Design

On a Path to Zero Energy Construction: Passive House & Building Workshop

John Semmelhack www.think-little.com AGENDA o HVAC goals o Heating, Cooling, Dehumidification o Ventilation o Single-family, mixed-humid climate focus HVAC GOALS o We don’t build buildings in order to save energy o Our first job is to provide comfort! o Indoor Air Quality – first, do no harm HEAT – COOL – DEHU AGENDA o PHIUS heating + cooling load standards o Load calculations o Equipment selection o Supplemental dehumidification? o Duct design PHIUS HEATING + COOLING METRICS PHIUS HEATING + COOLING METRICS

For a 2,500ft2 house:

10,000 Btu/hr heating load 12,250 Btu/hr cooling load

“1-ton” LOAD CALCULATIONS*

Why do we do load calcs?

* aka “Peak loads” or “Design Loads” LOAD CALCULATIONS

Why do we do load calcs?

Prior to selecting equipment, we need to know how much heat we need to add or remove in order to maintain comfort during peak/design conditions.

We’d like to pick equipment that’s neither too small (bad comfort) nor too big (higher cost and bad comfort) ……but just right! LOAD CALCULATIONS

Three loads:

1. Heating 2. Sensible cooling 3. Latent cooling (aka dehumidification) LOAD CALCULATIONS

Three loads:

1. Heating 2. Sensible cooling 3. Latent cooling LOAD CALCULATION METHODS

Manual J

o Room-by-room or block load o Typically uses 1% and 99% ASHRAE design temperatures o Incorporates solar and internal gains for cooling, but not for heating o Thermal mass/lag is accounted for in solar gains. The calculated peak solar gains are typically in the ballpark of 80-90% of the daytime average o Latent load calculation? YES! FACT SHEET FOR PH LOADS

Heating loads in Passive Houses are driven mostly by envelope performance and delta-T

Sensible cooling loads in Passive Houses are driven almost entirely by solar gains and internal gains

Latent cooling loads in Passive Houses are driven almost entirely by ventilation gains and internal gains

All houses will experience part-load sensible with peak latent on some days (cloudy + humid) FACT SHEET FOR PH LOADS

Heating loads in Passive Houses are driven by envelope performance and delta-T

Sensible cooling loads in Passive Houses are driven almost entirely by solar gains and internal gains

Latent cooling loads in Passive Houses are driven almost entirely by ventilation gains and internal gains

All houses will experience part-load sensible with peak latent on some days (cloudy + humid) FACT SHEET FOR PH LOADS Sensible cooling loads in Passive Houses are driven almost entirely by solar gains and internal gains

In some situations, peak solar gains can occur outside of the summer months! Dynamic/hourly calculation is probably needed for houses with excessive south glazing

Solar gains can be reduced by :

o Reducing window area o Lower SHGC o Better shading – especially operable/moveable

o FACT SHEET FOR PH LOADS

Heating loads in Passive Houses are driven by envelope performance and delta-T

Sensible cooling loads in Passive Houses are driven almost entirely by solar gains and internal gains

Latent cooling loads in Passive Houses are driven almost entirely by ventilation gains and internal gains

All houses will experience part-load sensible with peak latent on some days (cloudy + humid) FACT SHEET FOR PH LOADS

Latent cooling loads in Passive Houses are driven entirely by ventilation gains and internal gains

Assuming a fixed climate, internal gains and ventilation rate, the only option to reduce latent gains is to increase the moisture transfer rate on an ERV! FACT SHEET FOR PH LOADS

Heating loads in Passive Houses are driven by envelope performance and delta-T

Sensible cooling loads in Passive Houses are driven almost entirely by solar gains and internal gains

Latent cooling loads in Passive Houses are driven almost entirely by ventilation gains and internal gains

All houses will experience part-load sensible with peak latent on some days (cloudy + humid) FACT SHEET FOR PH LOADS

All houses will experience part-load sensible with peak latent on some days (cloudy + humid)

It’s useful to calculate the sensible heat ratio (SHR) for both peak sensible conditions (high solar gain) and part- load sensible conditions (low solar gain). Manual J doesn’t do this.

Controlled dehumidification may be needed. EXAMPLE HOUSE

30x30x20 – 1,800ft2 3-bed house with moderately-heavy south glazing and “OK” overhangs…

overhangs not shown! LOAD CALCULATIONS – Manual J LOAD CALCULATIONS – Manual J LOAD CALCULATIONS – Room loads (Manual J) LOAD CALCULATIONS – Room loads (Manual J)

Approx. 2 sleeping children + 1 LED nightlight LOAD CALCULATIONS – Room loads (Manual J)

Less than 50% of the lowest output on the smallest available mini-split LOAD CALCULATIONS – Room loads (Manual J)

How much non-ducted cooling can you get through an open door on the 2nd floor? LOAD CALCULATIONS – Room loads (Manual J)

How much non-ducted cooling can you get through an open closed door on the 2nd floor? EQUIPMENT SIZING + SELECTION

Manual J loads:

Heating: 7,934 Btu/hr Sensible Cooling: 9,020 Btu/hr Latent Cooling: 1,641 Btu/hr o Is there appropriate equipment available for these loads? o Do we need supplemental or backup heat? o Do we need supplemental dehumidification? EQUIPMENT SIZING + SELECTION

Manual J loads:

Heating: 7,934 Btu/hr Sensible Cooling: 9,020 Btu/hr Latent Cooling: 1,641 Btu/hr o How much money should we spend on equipment that provides just $100-200* worth of heat/cool per year? *energy cost o How do we make a choice? EQUIPMENT SIZING + SELECTION

Start with nominal- rated-nameplate capacity

Manual J loads: As low as As low as Heating: 7,934 Btu/hr 18,000 Btu/hr 9,000 Btu/hr (1.5 tons) Sensible Cooling: 9,020 Btu/hr (3/4 ton) Latent Cooling: 1,641 Btu/hr EQUIPMENT SIZING + SELECTION

What about multi-splits?

Manual J loads:

Heating: 7,934 Btu/hr Sensible Cooling: 9,020 Btu/hr Latent Cooling: 1,641 Btu/hr EQUIPMENT SIZING + SELECTION

What about multi-splits?

Manual J loads: Rated + minimum capacities as low as: Heating: 7,934 Btu/hr 18,000 - 8,000 Btu/hr for 2-head systems Sensible Cooling: 9,020 Btu/hr 24,000 - 13,000 Btu/hr for 3-head systems Latent Cooling: 1,641 Btu/hr 36,000 - 13,000 Btu/hr for 4-head systems EQUIPMENT SIZING + SELECTION

Isn’t oversizing “ok” for mini-splits?

NREL lab testing shows 20- 40% decrease in COP when units cycle on and off when load is below minimum capacity!

Manual J loads:

Rated + minimum capacities as low as: Heating: 7,934 Btu/hr Sensible Cooling: 9,020 Btu/hr 18,000 - 8,000 Btu/hr for 2-head systems Latent Cooling: 1,641 Btu/hr 24,000 - 13,000 Btu/hr for 3-head systems 36,000 - 13,000 Btu/hr for 4-head systems EQUIPMENT SIZING + SELECTION

In most single-family Passive Houses, standard heat pumps and multi-splits are too oversized for the loads. Low-capacity single mini-splits become the “choice”

Manual J loads:

Rated + minimum capacities Heating: 7,934 Btu/hr as low as 9,000 - 3,000* Btu/hr Sensible Cooling: 9,020 Btu/hr Latent Cooling: 1,641 Btu/hr *~5,000-6,000 Btu/hr according to NREL EQUIPMENT SIZING + SELECTION EQUIPMENT SIZING + SELECTION

How much capacity do they have at my design temperatures?

Need expanded performance data (aka “engineering data” or “capacity tables”) EQUIPMENT SIZING + SELECTION Manual J loads:

Heating @ 1F : 7,934 Btu/hr Sensible Cooling @ 89F DB : 9,020 Btu/hr Latent Cooling @ 73F WB: 1,641 Btu/hr EQUIPMENT SIZING + SELECTION Manual J loads:

Heating @ 1F : 7,934 Btu/hr Sensible Cooling @ 89F DB : 9,020 Btu/hr Latent Cooling @ 73F WB: 1,641 Btu/hr

63 SUPPLEMENTAL & BACKUP HEAT

Supplemental heat needed here SUPPLEMENTAL & BACKUP HEAT

Supplemental heat needed here

Excess heating capacity! SUPPLEMENTAL DEHUMIDIFICATION?

All houses will experience part-load sensible with peak latent on some days (cloudy + humid)

It’s useful to calculate the sensible heat ratio (SHR) for both peak sensible conditions (high solar gain) and part- load sensible conditions (low solar gain). Manual J doesn’t do this.

Controlled dehumidification may be needed. SUPPLEMENTAL DEHUMIDIFICATION?

Ducted or floor-standing “standard” dehumidifiers

http://www.thermastor.com/Ultra-Aire-70/ DUCT DESIGN: FAN POWER + STATIC PRESSURE

Ways to cut static pressure:

o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct FAN POWER + STATIC PRESSURE

Ways to cut static pressure: o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct FAN POWER + STATIC PRESSURE

Ways to cut static pressure: o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct

400 0.03

~90% less pressure drop = 30W less fan power at air handler = 3,000kWh savings over life of duct system FAN POWER + STATIC PRESSURE

Ways to cut static pressure: o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct

80’EL 900fpm FAN POWER + STATIC PRESSURE

Ways to cut static pressure: o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct

80’EL 900fpm

900fpm FAN POWER + STATIC PRESSURE

Ways to cut static pressure: o Lower velocity / larger duct o Aerodynamic fittings o Shorter lengths of straight duct

80’EL 900fpm

15’EL 900fpm FAN POWER + STATIC PRESSURE

Ways to cut static pressure:

oLower velocity / larger duct oAerodynamic fittings oShorter lengths of straight duct

There’s very little “low hanging fruit” left in a passive house! This is one piece… FAN POWER + STATIC PRESSURE

Ways to cut static pressure:

oLower velocity / larger duct oAerodynamic fittings oShorter lengths of straight duct

There’s very little “low hanging fruit” left in a passive house! This is one piece…

ERV example: 0.75W/cfm * 75cfm = 493kWh/yr 0.50W/cfm * 75cfm = 329kWh/yr FAN POWER + STATIC PRESSURE

Ways to cut static pressure:

oLower velocity / larger duct oAerodynamic fittings oShorter lengths of straight duct

There’s very little “low hanging fruit” left in a passive house! This is one piece…

ERV example: o 164kWh/yr savings! 0.75W/cfm * 75cfm = 493kWh/yr o 3% of whole house 0.50W/cfm * 75cfm = 329kWh/yr o A whole year of energy saved over 30 years! VENTILATION AGENDA o ERV + HRV equipment design goals o Pros + Cons compared to other ventilation systems o Energy + Non-energy benefits o To ERV or to HRV? o Equipment selection o System design o Airflow testing + balancing WHAT’S NOT ON THE AGENDA o Whether or not to ventilate o What’s the correct airflow rate? HRV: Heat Recovery Ventilator

ERV: Energy Recovery Ventilator

(formerly known as “Enthalpy”)

Key equipment design goals: o Highest heat transfer core o “Optimized” moisture transfer (if ERV) o Lowest fan power o “Capture” waste heat in winter, “reject” in summer o Minimize cross leakage and case heat exchange o Smallest package o Lowest cost Other equipment design goals: o Advanced fan speed controls / timers / sensors o Bypass / Economizer o Easy to install / commission o Easy to maintain o Defrost control o Low noise Pros + Cons Pros + Cons o Can reduce space conditioning operating costs* o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o Can reduce space conditioning operating costs o In some cases – can reduce space conditioning equipment capacity + costs o Balanced ventilation doesn’t effect building enclosure o Control over ventilation source o Ventilation source can be filtered o Easy to exhaust from multiple locations o Close to neutral temperature + humidity o Control over supply location/s Pros + Cons o $$ Cost $$ o Slightly more complexity To E RV o r t o H RV ?

It’s complicated - these are the considerations: o Climate o Ventilation rate o Enclosure air leakage rate o Occupant density + habits o ERV moisture transfer rate To E RV o r t o H RV ?

It’s complicated - these are the considerations: o Climate o Ventilation rate o Enclosure air leakage rate o Occupant density + habits o ERV moisture transfer rate

In some cases, it would be ideal to have an HRV in the winter and an ERV in the summer! Does an ERV/HRV?…

o Provide make-up air for large exhaust fans o Reduce stratification in a house o Spin straw into gold Equipment selection

Key equipment selection criteria: o Highest “net” heat transfer % o Lowest fan power o “Optimized” moisture transfer (if ERV) o Appropriate airflow rates for your project o Smallest package o Lowest cost Equipment selection

www.hvi.org www.ahridirectory.org

www.phius.org/Tools-Resources/Protocols-Calculators/HVI-Winter-Ratings- modified-for-PHIUS-modeling_June2016.xls System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation System design considerations o Access for service / maintenance / testing o Filters to protect core o Filters for IAQ o Balancing dampers o Condensate drain for HRVs o Defrost strategy for HRVs (and ERVs in some climates) o Location – noise mitigation Airflow distribution

Ducts connected to the outside: o 10’ separation at exterior hoods o OA intake hood above historical snow level o Wire screens on exterior hoods o Motorized dampers or backdraft dampers if system will run intermittently o Insulated ductwork + vapor barrier wrap to prevent condensation o Minimize duct length o Tight ducts Airflow distribution

Ducts connected to the outside: o 10’ separation at exterior hoods o OA intake hood above historical snow level o Wire screens on exterior hoods o Motorized dampers or backdraft dampers if system is designed to run intermittently o Insulated ductwork + vapor barrier wrap to prevent condensation o Minimize duct length o Tight ducts Airflow distribution

Ducts connected to the inside: o Supply air to where the people are o Exhaust air from where the people generate moisture + other pollutants o Optimize duct design based on design flow rates and fan flow curve o Use silencers, flex duct or duct liner to minimize sound transmission o Don’t blow air on people o Tight ducts Airflow distribution

Can I connect my ERV to my heating/cooling ducts? Airflow testing / balancing

Total airflow balancing: o Total supply and total exhaust meet design values and are within 10% of one another o Test at exterior hoods, in duct, or via built -in pressure ports – need appropriate tools! o Test on a calm day, if possible Airflow testing / balancing

Branch balancing: o Each branch must include a damper! o Use a powered flow hood for supplies o +/- 5cfm from design value Thank you for your attention!

Questions? [email protected]