special vents | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Author	Comments
Eric Sparks Posted: Apr 04, 2009 01:03 PM	special vents I had a builder - contractor tell me that a special vent is needed when sealing a structures envelope so the structure can breath. I believe he called it a erv vent or something similsr sounding. What is he talking about, is this something new. Thanks
mason Posted: Apr 05, 2009 09:26 AM	He is referring to an energy recovery ventilation system. This brings "make up" air into the building if the building is sealed "too tight" with air barrier materials. Whether an ERV is required is dependent on how many air exhanges the building has after the sprayfoam application. In most retrofit situations, there is still enough "natural" air leakage to have adequate air exchanges per hour, but in new construction it is typical that the application of sprayfoam would seal the building so tight that additional make up air would be required. Note; the ERV not only brings in make up air for the HVAC system but also conditions the air to the desired temperature, filters it and helps redistribute it to the appropriate areas of the building. By the way, an ERV will add cost to the project, in some cases "make up" air can be brought into the ventilation system without the use of an ERV. But the ERV is more energy efficient. The air exchange rate of a building is measured byh performing a blower door test or in the case of large structures by using the existing HVAC system to pressurize the building and measuring the air exchanges. If you are working with buildings that have similar constructon designs, and air tightness, you may be able to use a couple of blower door tests to estimate the air exchanges in the rest of the buildings. For example, a tract home builder would use this method instead of performing blower door tests on each house to determine its ventilation needs. Hope this helps.
SprayFoamSupply.com Posted: Apr 05, 2009 10:21 AM	There will be a presentation on air exchangers as part of our conference on May 7 at 4:30. See link at left for schedule. George
mason Posted: Apr 05, 2009 11:56 AM	Great! It is a subject that is easily misunderstood in the building community. I am looking forward to learning more about them.

Author

Comments

Eric Sparks

Posted: Apr 04, 2009 01:03 PM

special vents

I had a builder - contractor tell me that a special vent is needed when sealing a structures envelope so the structure can breath. I believe he called it a erv vent or something similsr sounding. What is he talking about, is this something new. Thanks

mason

Posted: Apr 05, 2009 09:26 AM

He is referring to an energy recovery ventilation system. This brings "make up" air into the building if the building is sealed "too tight" with air barrier materials.

Whether an ERV is required is dependent on how many air exhanges the building has after the sprayfoam application. In most retrofit situations, there is still enough "natural" air leakage to have adequate air exchanges per hour, but in new construction it is typical that the application of sprayfoam would seal the building so tight that additional make up air would be required.

Note; the ERV not only brings in make up air for the HVAC system but also conditions the air to the desired temperature, filters it and helps redistribute it to the appropriate areas of the building. By the way, an ERV will add cost to the project, in some cases "make up" air can be brought into the ventilation system without the use of an ERV. But the ERV is more energy efficient.

The air exchange rate of a building is measured byh performing a blower door test or in the case of large structures by using the existing HVAC system to pressurize the building and measuring the air exchanges. If you are working with buildings that have similar constructon designs, and air tightness, you may be able to use a couple of blower door tests to estimate the air exchanges in the rest of the buildings. For example, a tract home builder would use this method instead of performing blower door tests on each house to determine its ventilation needs.

Hope this helps.

SprayFoamSupply.com

Posted: Apr 05, 2009 10:21 AM

There will be a presentation on air exchangers as part of our conference on May 7 at 4:30. See link at left for schedule.

George

mason

Posted: Apr 05, 2009 11:56 AM

Great! It is a subject that is easily misunderstood in the building community. I am looking forward to learning more about them.

You need to login to reply to this topic. Please click here to login.