Mechanical Ventilation

Modified on Wed, 6 Sep, 2023 at 5:23 PM

Mechanical Ventilation Library Help

If you don't know the manufacturers specifications for ventilation systems, you can check the Home Ventilating Institute's Certified Products Directory.

Type

Options include:

Exhaust Only - One or more exhaust fans (commonly located in bathrooms and/or kitchens) that either continuously or intermittently remove air from the home.
Supply Only - An indoor fan that brings in air from outside and distributes it throughout the home.
Balanced - A combination of exhaust and supply ventilation that simultaneously balances air flowing into and out of the home, keeping the indoor pressure constant.
ERV - Energy-Recovery Ventilators utilize a balanced ventilation strategy, and recover both sensible and latent heat during air exchange.
HRV - Heat-Recovery Ventilators are a simpler sub-type of ERVs, that recover only sensible heat during air exchange.
Air Cycler - Supply-duct integrated ventilation using the central air handler with electronically controlled dampers. Also known as Central Fan Integrated Supply (CFIS) systems. Ekotrope will only account for fan energy beyond what would normally be consumed by the air handler.
Air Cycler w/ Supp. Fan - This is similar to a traditional Air Cycler system, but when ventilation is necessary at times that the air handler is not already on, ventilation is provided by a supplemental fan (e.g. a bathroom exhaust fan) that is wired to the Air Cycler control system rather than by the air handler itself. For these systems, the Fan Watts specified should be the Watts for the supplemental fan, not for the air handler.

Ventilation Rate

Enter the mechanical ventilation rate in [Cubic Feet / Minute]. Reference ASHRAE Standard 62.2 for recommended ventilation rates.

Fan Watts

If the rated or measured wattage of the ventilation fan is known specify it here. If it isn't known, you may select the "Use Default Fan Watts" checkbox, which will satisfy RESNET Addendum 39.

For Central Fan Integrated Systems (CFIS, aka Air Cyclers) without a supplemental fan, enter the wattage consumed by the air handler at the design ventilation rate. The design ventilation rate is not the full design flow of the air handler, it is the rate of controlled outside air for Indoor Air Quality. For Air Cyclers with a supplemental fan enter the wattage of the supplemental fan, not the air handler.

From ANSI/RESNET Standard 301-2014 Addendum 39
To determine fan energy in the Rated Home, ventilation fan watts shall be based on the table below for the given system or the value observed in the Rated Home, for the highest airflow setting. Where needed to calculate fan watts, for systems other than Central Fan Integrated Supply (CFIS), the Whole-House Mechanical Ventilation System rate shall be assumed to be equal to Qfan, as calculated in accordance with Section 4.1.2 of ASHRAE Standard 62.2. For CFIS systems, the cfm used to determine fan watts shall be the larger of 400 cfm per 12 kBtu/h cooling capacity or 240 cfm per 12 kBtu/h heating capacity.

Default Ventilation Fan Watts
Equipment Type	Watts/CFM
Exhaust ventilation fans	0.35
Supply ventilation fans	0.35
Balanced ventilation fans	0.70
HRV/ERV fans	1.00
CFIS fans	0.50
Range hoods	0.70

Operational Hours per Day

Enter the number of hours the fan is running per day.

Runs Once Every Three Hours

This box should be checked if intermittent ventilation runs at least once every three hours. This will not affect the energy consumption or HERS Index of the home, but it will affect the ASHRAE 62.2 required ventilation calculation. ASHRAE 62.2 specifies a different ventilation effectiveness for fans that run at least once every 3 hours.

If ERV or HRV are selected for type then the following field will also be available:

Energy Recovery Percent

Specify the Adjusted Sensible Recovery Efficiency (ASRE) of the ERV or HRV. If using the HVI directory, this will be in a row listed HEATING. If there are multiple rows, please select the ASRE with the corresponding temperature and fan flow that most closely reflects the climate and fan speed that will be present.