ERV/HRV required? | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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Robert Hughes Posted: May 13, 2008 09:20 PM	ERV/HRV required? I know this has been talked about in various forums but I have yet to find an answer that seems clear for my region. 1. For new construction, full building envelope jobs: I have read that an ERV/HRV system is required on all foamed houses. You know, "build it tight - ventilate it right..." Is this accurate in the South, being a mostly hot region? I am curious because nobody is doing this here. Most are spraying .5 lb foam on the walls and roof-deck, with typically no modifications to the HVAC other than downsizing. 2. In retrofit situation with sprayed roof-deck, converted from vented to un-vented hot roof system: We completed one job where the owner did not want to us remove the existing sprayed-in attic floor insulation. He has since complained that his attic is extremely hot and his energy costs are actually higher now. I have told him that we should at least remove the old insulation, to allow some air infiltration from the house to the attic as a first step. Now I am thinking an HRV/ERV system might be step 2. Does this seem like the right approach? Thanks.
mason Posted: May 13, 2008 10:17 PM	You may or may not need make up air when foaming a house. It depends on the amount of natural ventilation after foaming. For example, if the windows and doors leak a lot of air, foaming is not going to seal the building as tight. Also, retrofit work doesn't seal as well as new construction. It really is on a case by case basis. The HVAC contractor would probably know the different types of construction in your area and can make recommendations. Foaming the house will reduce air infiltration around 30 to 50% in most new construction. For example if the house normally would have .55 air exchanges per hour, a totally foamed house would have between .20 and .35 air changes per hour. They can make the decision if a HRV is required.
Rob Granger Posted: May 15, 2008 09:39 PM	Texas Spray Foam, Whether your in the hot weather of the South or the cold weather of the North it is best to control your air infiltration and exfiltration. If you do your heat/cooling cost will be minimal, the whole reason we are pushing spray foam. When we spray a new house we tighten it up even further by caulking the top and bottom plate, headers, and multiple stud intersections. We additionally foam with orange fire resistant can foam all penetrations at the floor and ceiling plane. If we could absolutely tighten it up we would. Now that it is tight we have to install a ventilation system for health and safety reasons. Indoor air quality is important for the occupants. The EPA requires a .278 air changes per hour. BPI reccommends .35 air changes per hour. The only way you can know your air changes is to do a blower door test on the house. The calculation is .35 x Volume of the house / 60. That would be the Base Line. Below 70% of this figure ventilation is required. Between 70% & 100% ventilation is reccommended. I would disagree with Mason in that most HVAC contractors do not know building performance science. Call your state energy regulatory agency or call Building Performance Institute for more information. The energy codes are going to change in significant ways in the next several years and if you want to be in on the ground floor get your certification as a building performance technician. It will gain you much business and credibility as a spray foam guy. I was the high bidder on my current job but I got it because the owner, an engineer said I knew what I was talking about... Be the leader in your area not the follower...............
mason Posted: May 17, 2008 07:33 AM	Yes, I would hesitate to take on the job of the mechanical contractor without getting the required training and credentials. Most foamers are not HVAC contractors. For liability sake be sure you know what you are doing before getting too much involved in designing ventilating systems for houses and commercial buildings. The typical sprayfoam contractor should develop relationships with local mechanical contractors that know how to design around foam insulated buildings. They can assist when you get into a situation with another HVAC contractor who is not familiar with foam and provide the calculations for that specific job. (In some cases they can get extra work out of it, plus they can feed work back to you.) Blower door tests are great, but can be pricey if used on every job. If you work with specific builders, you can spot check homes to verify the relative degree of leakiness in that type of construction. But definitely let the HVAC contractor know that foam will tighten up the building significantly. If they don't have a clue, let the owner know about it, so they can be aware.
Rob Granger Posted: May 17, 2008 08:36 PM	Mason, Thanks for re-emphasizing to all of the foamers that they should get training before educating others about building performance. It is exactly what I am suggesting. This energy crisis in the way of high heat & cooling bills is here to stay and because of it more people will get into the spray foam business. If you differentiate your self from the others you will weather the storm and prosper beyond your dreams. Many states are becoming serious about decreasing our demand for energy that our homes and buildings consume. States are giving grants and low energy mortgages to people who desire to reduce their energy costs and they are looking for contractors to do the work. This will mean evaluating a house based on many fronts.... but will ultimately lead to work spray foaming attics, injecting foam in walls, air sealing, recommending heating equipment replacement and more, but you cannot do this work in many states unless you are certified. Adding insulation or even just spray foaming a new house effects a house in other ways. Generally a new house with foam is to tight - Ventilation is then required for health reasons. Remember what those old timers say even today - you can get a house to tight!! But remember if you control the ventilation then you control the energy cost for the house. Mason, I can tell you when you need ventilation and certainly how much beacuse I am trained and certified to use a blower door, a duct blaster, and much more but I leave the sizing of the unit to an engineer also trained to do so. All you foamers google Building Performance Institute. Consider getting their certification. Also call your state energy office and see what I am talking about - where we are headed as an industry and if you want to be involved....
mason Posted: May 18, 2008 06:47 PM	Good advice Yes, I concur completely. The better you are informed and trained, the more likely the job will turn out right.

Author

Comments

Robert Hughes

Posted: May 13, 2008 09:20 PM

ERV/HRV required?

I know this has been talked about in various forums but I have yet to find an answer that seems clear for my region.

1. For new construction, full building envelope jobs:

I have read that an ERV/HRV system is required on all foamed houses. You know, "build it tight - ventilate it right..."

Is this accurate in the South, being a mostly hot region?

I am curious because nobody is doing this here. Most are spraying .5 lb foam on the walls and roof-deck, with typically no modifications to the HVAC other than downsizing.

2. In retrofit situation with sprayed roof-deck, converted from vented to un-vented hot roof system:

We completed one job where the owner did not want to us remove the existing sprayed-in attic floor insulation. He has since complained that his attic is extremely hot and his energy costs are actually higher now.

I have told him that we should at least remove the old insulation, to allow some air infiltration from the house to the attic as a first step.

Now I am thinking an HRV/ERV system might be step 2. Does this seem like the right approach?

Thanks.

mason

Posted: May 13, 2008 10:17 PM

You may or may not need make up air when foaming a house. It depends on the amount of natural ventilation after foaming. For example, if the windows and doors leak a lot of air, foaming is not going to seal the building as tight. Also, retrofit work doesn't seal as well as new construction. It really is on a case by case basis. The HVAC contractor would probably know the different types of construction in your area and can make recommendations. Foaming the house will reduce air infiltration around 30 to 50% in most new construction. For example if the house normally would have .55 air exchanges per hour, a totally foamed house would have between .20 and .35 air changes per hour.

They can make the decision if a HRV is required.

Rob Granger

Posted: May 15, 2008 09:39 PM

Texas Spray Foam,
Whether your in the hot weather of the South or the cold weather of the North it is best to control your air infiltration and exfiltration. If you do your heat/cooling cost will be minimal, the whole reason we are pushing spray foam. When we spray a new house we tighten it up even further by caulking the top and bottom plate, headers, and multiple stud intersections. We additionally foam with orange fire resistant can foam all penetrations at the floor and ceiling plane. If we could absolutely tighten it up we would. Now that it is tight we have to install a ventilation system for health and safety reasons. Indoor air quality is important for the occupants. The EPA requires a .278 air changes per hour. BPI reccommends .35 air changes per hour. The only way you can know your air changes is to do a blower door test on the house. The calculation is .35 x Volume of the house / 60. That would be the Base Line. Below 70% of this figure ventilation is required. Between 70% & 100% ventilation is reccommended. I would disagree with Mason in that most HVAC contractors do not know building performance science. Call your state energy regulatory agency or call Building Performance Institute for more information. The energy codes are going to change in significant ways in the next several years and if you want to be in on the ground floor get your certification as a building performance technician. It will gain you much business and credibility as a spray foam guy. I was the high bidder on my current job but I got it because the owner, an engineer said I knew what I was talking about... Be the leader in your area not the follower...............

mason

Posted: May 17, 2008 07:33 AM

Yes,

I would hesitate to take on the job of the mechanical contractor without getting the required training and credentials. Most foamers are not HVAC contractors. For liability sake be sure you know what you are doing before getting too much involved in designing ventilating systems for houses and commercial buildings.

The typical sprayfoam contractor should develop relationships with local mechanical contractors that know how to design around foam insulated buildings. They can assist when you get into a situation with another HVAC contractor who is not familiar with foam and provide the calculations for that specific job. (In some cases they can get extra work out of it, plus they can feed work back to you.)

Blower door tests are great, but can be pricey if used on every job. If you work with specific builders, you can spot check homes to verify the relative degree of leakiness in that type of construction.

But definitely let the HVAC contractor know that foam will tighten up the building significantly. If they don't have a clue, let the owner know about it, so they can be aware.

Rob Granger

Posted: May 17, 2008 08:36 PM

Mason,
Thanks for re-emphasizing to all of the foamers that they should get training before educating others about building performance. It is exactly what I am suggesting.

This energy crisis in the way of high heat & cooling bills is here to stay and because of it more people will get into the spray foam business. If you differentiate your self from the others you will weather the storm and prosper beyond your dreams. Many states are becoming serious about decreasing our demand for energy that our homes and buildings consume. States are giving grants and low energy mortgages to people who desire to reduce their energy costs and they are looking for contractors to do the work. This will mean evaluating a house based on many fronts.... but will ultimately lead to work spray foaming attics, injecting foam in walls, air sealing, recommending heating equipment replacement and more, but you cannot do this work in many states unless you are certified.

Adding insulation or even just spray foaming a new house effects a house in other ways. Generally a new house with foam is to tight - Ventilation is then required for health reasons. Remember what those old timers say even today - you can get a house to tight!! But remember if you control the ventilation then you control the energy cost for the house.

Mason, I can tell you when you need ventilation and certainly how much beacuse I am trained and certified to use a blower door, a duct blaster, and much more but I leave the sizing of the unit to an engineer also trained to do so.

All you foamers google Building Performance Institute. Consider getting their certification. Also call your state energy office and see what I am talking about - where we are headed as an industry and if you want to be involved....

mason

Posted: May 18, 2008 06:47 PM

Good advice Yes, I concur completely. The better you are informed and trained, the more likely the job will turn out right.

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