Fresh-Air Ventilation

An air-tight, low-energy building in this climate should include dedicated mechanical ventilation with heat-recovery in order to deliver enough fresh air for good indoor air-quality (IAQ) in all seasons.

Supply fresh air to bedrooms and living spaces, extract from kitchens and bathrooms. Allow for a transfer pathway between zones.


It is important not to over-ventilate a building in winter, otherwise over-dry indoor air and associated health concerns can result. In order to help reduce airflow rates while still maintaining good indoor air-quality, we recommend using a Supply- Transfer-Extract configuration rather than supplying and extracting from each individual room. Supply air should be provided to bedrooms and living spaces, while extract air should be drawn from bathrooms, the kitchen, and any storage spaces. Transfer openings (door undercuts, transfer grills, etc...) should be provided between supply and exhaust spaces.

This configuration reduces the potential for any duct-born sound transmission between spaces, ensures a good mixing of the fresh air supply, and reduces the size, complexity and cost of the ducting required.

Fresh-Air Ventilation Flow Rates

In order to establish good airflow rates for the building which both provide sufficient fresh-air but do not over-ventilate, we recommend a three-part test for sizing fresh air ventilation flow-rates to individual spaces. The larger of the three resultant flow-rates should be used as the design flow rate when selecting an appropriate E/HRV model.

  1. Test for Minimum Supply air flow rate:
    Flow rates should be based on a standard 18 cfm/person occupancy. The occupancy is based on a ‘typical’ 375 sf/person rate unless otherwise specified. This flow rate is designed to provide good indoor air-quality without causing excessive energy-loss or over-dry air (winter) or excess humidity (summer).
  2. Test for Minimum Extract air flow rate:
    Based on the space usage (Kitchen, Bath, Storage, etc..) establish minimum extract rates. These rates should be as follows: 36 cfm/ kitchen, 26 cfm/full bathroom, 12 cfm/storage or utility room.
  3. Test for a Minimum whole-building ACH @ 100% fan speed:
    The minimum flow rate for any building should be 0.39 ACH in winter at 100% HRV fan speed. This is for hygienic reasons, even if the occupancy or space usage would lead to a smaller flow-rate this minimum takes precedence.

The largest of the above values should be used in order to establish target design flow-rates for the building. We have evaluated the building using this method and recommend fresh-air flow rates according to the schedule below.

Fresh-Air Ventilation System Target Flow Rates

Fresh-Air Ventilation System Diagram | Basement Level


Supply Air Zones
Extract Air Zones
Transfer Air Zones
Ventilation Floor Plan - Basement

Fresh-Air Ventilation System Diagram | First Floor


Ventilation Floor Plan - First Floor

Fresh-Air Ventilation System Diagram | Second Floor


Ventilation Floor Plan - Second Floor

Fresh-Air Ventilation System Diagram | Attic Level


Ventilation Floor Plan - Attic

Ventilation Components

ERV UNIT

Zehnder Q600 ERV installed in a closet

For this home, we recommend a high performance H/ERV unit with better than 75% heat recovery. The Zehnder America ComfoAir Q600 unit would be a good selection and provide excellent Indoor Air Quality while minimizing energy consumption and heat loss. This unit is outfit with excellent air filtration (MERV 13) by default which will be critical to ensuring clean and healthy indoor air. In addition, Zehnder America will provide a full balance of system specification with all ducting, dampers, diffusers and registers needed for the home in one package which greatly simplifies design and installation.

Note that Zehnder America should also be retained to balance and commission the system after installation. This is critical for proper operation and required for Passive House certification. This service will normally come standard with all Zehnder America packages but this should be verified in this case.

SYSTEM BALANCING


Prior to occupancy, the fresh-air system should be tested and balanced to ensure good air mixing and adequate supply to all living spaces. The HRV vendor should provide this balancing as part of their services.

ERV airflow testing use an anemometer ERV ducting damper element

Image Source: http://www.greenbuildingadvisor.com/blogs/dept/ energy-solutions/commissioning-our-heat-recovery-ventilator Alex Wilson, BuildingGreen, Inc

ALTITUDE TRAINING DEVICES AND VENTILATION REQUIREMENTS


For rooms designated for altitude training, special attention should be paid to the fresh-air delivery and exchange strategy specific to those designated spaces. Technical issues such as oxygen transfer, mechanical heat rejection, and equipment location should be considered in the larger context of mechanical ventilation system planning.

Hypoxico HYP 123 Generator

Image Source: Hypoxico

Appliances and Venting

KITCHEN VENTING

If Kitchen hood venting is desired or required by code, exhaust flow should be limited to the lowest level allowable. For gas cooking, this flow rate will be specified by code. For electric cooking, limit exhaust hood airflow to 200-400 cfm maximum through the selection of an appropriately sized hood. If flow rates greater than 200 cfm are desired, a makeup air and control strategy should be used for the extract and a supply fan to ensure flow balance. A tempering pre-heater should be included in the supply air duct in order to ensure occupant comfort during cold-weather conditions. Envelope penetrations should be carefully configured and airtightness at all penetrations must be maintained. Minimum inlet / outlet separation requirements should be followed and envelope penetrations should be coordinated with the architectural finishes. Inlet and outlet ducts should be fitted with self-closing (magnetic) dampers to prevent air infiltration/exfiltration when the fans are not in use.

Kitchen makeup air should be supplied primarily into crawlspaces or mechanical zones. Ensure all dampers are switched to the exhaust hood and provide makeup air heating as needed.
1
2
3

Several things should be kept in mind when configuring such a system:

  1. Ensure airtightness at all envelope penetrations.
  2. All ducting insulated with vapor-closed insulation (min 2”) and vapor-closed tape all joints.
  3. Provide no more than 60% of the make-up air at base of range/oven.
  4. For Gas cooking, follow all local code requirements and manufacturer’s instructions.

CLOTHES DRYERS

In place of traditional venting clothes dryers, non-venting (heat pump condensing) dryers can be used which require no venting, fans, controls, sensors, dedicated exhaust or make-up air systems. We strongly recommend utilizing non- venting appliances. The best resource for finding high-performance appliances in the US is the EnergyStar Online Product Finder. This database includes many types of appliances but in particular have several high-performance heat-pump non-venting driers which are very good solutions for most types of residential buildings.

Energy Star website image

MAKEUP AIR SYSTEMS


In order to properly vent any exhaust air appliances (clothes dryers, kitchen hoods, etc.) in an airtight home a dedicated makeup air system is necessary with the appropriate controls. In this scenario, makeup air from an automatic makeup air fan is used to balance out the exhausted air.

Note that for most cases we do NOT recommend this strategy as it is costly, complicated, and adds considerable complexity to the envelope construction (insulation, air-sealing) and represents a significant energy penalty to heat/cool the makeup air. Wherever possible, the use of modern non-venting appliances should be considered.

Heating / Cooling of this outdoor air may be needed once it enters the habitable space. Self-closing (magnetic) dampers should be included on all ducting to prevent air infiltration / exfiltration when the appliances are not in use. In order not to compromise occupant comfort when makeup air is being supplied to the home, a high output heating element will need to be sized and installed to heat the incoming volume of air to a comfortable temperature. Electro Industries makes an excellent, self-modulating makeup air system (MUAS) and corresponding makeup air heater (MUAH) which could be a good fit for this project.

Magnetic damper for dryer exhaust

To ensure no air leakage occurs through the ducting when the exhaust appliances are off, an exterior damper (magnetic) should be used. American Aldes has a suitable damper product which is designed to remain closed under 75 Pa pressure and can work well for most applications.

<

Fireplace Recommendations

Based on initial discussions, we acknowledge the intent to retain the masonry fireplace for occasional wood fires. The appeal of a wood fire is understood, but indoor fireplace operation contributes to poor indoor air quality with a higher risk of unhealthy NOx and CO levels, as well as high concentrations of particulate matter which can exacerbate respiratory problems for occupants during use.

If open fireplaces are to be used, the occupants should understand that there may be negative health outcomes as a result and should take measures to reduce this risk as far as possible. In particular, occupants should be encouraged to follow the HPBA Responsible Wood burning guidelines which include:

  • Never leave a fire unattended. Extinguish any fire completely before leaving the room or going to bed for the night.
  • Ensure the home has multiple working CO detectors relatively proximate to the fireplace.
  • Inspect and maintain the chimney regularly
  • Monitor smoke development in the home carefully
  • Use only dry, seasoned wood
  • Use softwood instead of hardwood for smaller, more manageable fires
  • Where possible, ensure the fireplace equipment meets the EPA Certification rules
  • Consider running power to the top of the chimney for the future installation of a draft inducer. If the fireplace produces more smoke than desired in the home, consider installing this equipment.
  • Never use any venting appliances (dryers, kitchen venting hood) while the fireplace is being used. This could cause depressurization of the home and back drafting of smoke and contaminants down the chimney.

    • Follow all local code requirements for construction and venting. Note in particular:
  • IRC 1001.7.1: Masonry Fireplaces shall be equipped with a ferrous metal damper located no less than 8 inches above the top of the fireplace opening. Dampers shall be installed in the fireplace or the chimney venting the fireplace, and shall be operable from the room containing the fireplace.
  • IRC 1006.2: The exterior air intake shall be capable of supplying all combustion air from the exterior of the dwelling or from spaces within the dwelling ventilated with outdoor air such as nonmechanically ventilated crawl or attic spaces. The exterior intake shall not be located within the garage or basement of the dwelling. The exterior air intake, for other than factory-built fireplaces, shall not be located as an elevation higher than the firebox. The exterior air intake shall be covered with corrosion-resistant screen of 1/4" mesh.
  • IRC 1006.2 Exterior Air Intake: The exterior air outlet shall be located in the back or side of the firebox chamber or shall be located outside of the firebox opening. The outlet shall be closable and designed to prevent burning material from dropping into concealed combustion spaces.
  • IECC R402.4.2 Fireplaces: New wood-burning fireplaces shall have tight-fitting flue dampers or doors, and outdoor combustion air. Where using tight-fitting doors on factory-built fireplaces listed and labeled in accordance with UL 127, the doors shall be tested and listed for the fireplace


In place of open fireplaces, we recommend considering closed 'insert' fireboxes which can achieve a similar aesthetic effect but with better controllability and dedicated combustion air which reduces the risk of negative indoor air quality effects. Due to the efficient design of the home, we recommend to use the smallest firebox which meets the design goals of the home. In all likelihood, even the smallest unit available will be significantly oversized for the home's heating need and the occupants will likely find that they may need to open a window during use in order to reduce overheating of the space.

For any insert used, prioritize units with good air sealing and tightly fitting front doors. In addition, any unit used should have dedicated combustion air (rather than use the air from the indoor space) via dedicated ducting to each unit. If possible, any unit should meet the EPA Woodstove Certification requirements and all EPA recommendations.

Some units which may be suitable for this home include:

Example of Fireplace Insert with Stone surround

Heating and Cooling System

Manual J Calculations


A draft peak heating and cooling load calculation was done for the recommended version Wrightsoft's Right Suite Universal 2021 to perform calculations according to the Air Conditioning Contractors of America (ACCA) Manual J.

Graphs from Manual J Report

Based on these preliminary results, we have sized a heating/cooling system from Mitsubishi's M-Series. This split-system heat pump is designed to work even with the coldest outdoor temperatures using Mitsubishi's Hyper Heat technology. The system consists of a wall, ground or roof-mounted outdoor unit and horizontally poistioned indoor units. Ductwork distributes the heating and cooling throughout the building.

Mitsubishi MXZ-4C36NAHZ2 outdoor unit Mitsubishi SVZ-KP12NA ducted indoor unit











Please note: current system sizing is for pricing only. All peak load calculations must be updated once final decisions have been made regarding assemblies, windows, etc.

Domestic Hot Water

Rheem Performance Platinum ProTerra Hybrid

An excellent option for hot domestic hot water production for this poroject is an all-in-one air source heat pump (ASHP) such as the Rheem XE65T10HS45U0. This unit uses a simple design where the heating element is mounted directly on the tank making installation a bit easier to install and maintain than other 'split' heat-pump configurations. This unit is powered by electricity, making it cleaner and healthier than oil/gas fired options, and has a very high level of energy efficiency.

A unit such as this one could be installed in the basement without the need for additional ducting. The unit will provide some cooling and dehumidification of the space – a benefit in summer, but a slight energy penalty in winter. If the unit is installed in a smaller enclosure (e.g, a closet or small utility room), the unit would need to be ducted to an adjacent room. For details on the ducted installation refer to the manufacturers instructions page 12-13.

Rheem Heat Pump

Building Monitoring

Environmental Monitoring


There are several systems available for monitoring the temp, RH, CO2 and other environmental conditions. We strongly recommend installing a system of some form in order to successfully commission the home and correct any issues with indoor comfort over the first year. Environmental monitoring systems are relatively low cost, and we recommend 2 possible systems, the Wireless Sensor Tag by Cao Gadgets LLC, and the Netatmo weather-station. Both systems upload data to the internet over a wireless network and data can be accessed online. (Note: this requires a wireless network to be in operation at the home at all times)

The Wireless Tag system is less costly, but can not monitor CO2, and for this reason we would prefer the Netatmo system.

More information can be found at:
WirelessTag.net
www.Netatmo.com

Netatmo monitoring unit

Energy Monitoring

To really understand a home’s energy use, a branch circuit monitoring system is the way to go. Systems such as the Curb energy monitor provide customizable, real-time monitoring of electrical usage. The web/app based interface displays detailed information about the home’s energy usage and can help to fine-tune energy conservation measures.

More information can be found at: EnergyCurb.com

Curb energy monitoring system
Curb energy monitoring dashboard example