schlick
New Member
Posts:6
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| 22 Apr 2011 01:12 PM |
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I'm in the proccess of having a new home built with a estimated HERS rating of 45 with a 2ton gethermal unit and a exhaust system (using bath fans) that exhaust at rate of 90cu/ft a min per energy quidlines. My issue is with fresh air intake. There was none planed wich was strange to me so I did research and definitely need some. I was thinking of going the passive inlet route. Since i already have the exhaust I dont see the need for an ERV or HRV. Whats your thoughts on types of passive inlets and types. Thanks for the help |
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jonr
Senior Member
Posts:5341
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| 22 Apr 2011 01:50 PM |
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When you do the math, you find that it takes a huge passive intake to make up for an active exhaust and keep building pressure neutral. I suggest balanced fans, in and out.
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Rosalinda
Basic Member
Posts:353
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| 22 Apr 2011 02:15 PM |
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And then there are WINDOWS - they make great air intakes in many situations
But that depends on climate and air quality - so where is this house in regard to climate etc ?
-Rosalinda |
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| Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified |
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schlick
New Member
Posts:6
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| 22 Apr 2011 02:37 PM |
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It's located in Nebraska. The Panasonic FV-GKF32S1 claims 12cuft a min. If I install 4 i would be at 48 and the the other 40 could probably come from natural leakage. The cost for four would run me $200. I need to keep the aditional cost down. Trying to figure out the best option. |
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jerkylips
Basic Member
Posts:359
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| 22 Apr 2011 03:02 PM |
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Posted By schlick on 22 Apr 2011 02:37 PM
It's located in Nebraska. The Panasonic FV-GKF32S1 claims 12cuft a min. If I install 4 i would be at 48 and the the other 40 could probably come from natural leakage. The cost for four would run me $200. I need to keep the aditional cost down. Trying to figure out the best option. are you planning to leave these running all the time? An obvious point, but you're only moving 48 cfm while the fans are running. Also, bath fans have no heat exchanging capabilities - seems like you're going to be dumping a lot of conditioned air.. |
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Rosalinda
Basic Member
Posts:353
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| 22 Apr 2011 03:46 PM |
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During the summer I use windows but for the winter I am building a solar preheat box utilizing a 4 inch Tamarack cape back draft damper, that I am going to install on the inside of one of my windows. Wont know how well it works until next year around this time. I have a Panasonic FV-13VKS2 that I am using for whole house air quality, in addition to bathroom and kitchen vent fans. I plan on running it as needed based on humidity readings, and only during the day in winter, and hopefully only on sunny days to mitigate heat loss. The air intake should only open when negative pressure from running the vent fans opens it.
I also looked at units like these - http://www.tamtech.com/store/dream-aire-5000-air-filtering-filter-hrv,Product.asp
-Rosalinda |
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| Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified |
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schlick
New Member
Posts:6
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| 22 Apr 2011 03:50 PM |
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The Panasonic FV-GKF32S1 is only a passive intake. The 48cfm is at static pressure and would be higher with the exhust fans running. The exhaust fan will be a panasonic fan that is rated to run continusly at preset level between 0-110 and a bost of 130 with the switch on. I'm trying to reduce the negative pressure that is present in exhaust only systems but yet have and effiecient home.
HRV and ERV systems seem to have a very long payback period (25+ yrs is what I have been told) for a couple of reasons. 1) The cost. 2) wattage use. The fan runs between 15-25watts and the geo fan would be in the range of 350watts. 3) In research and talking with HVAC and Energy Raters there is very little heat exchange that takes place in ERV&HRV. 4) I'm tied to the bath fans because of the loan that I have optained, I can't deviate from the plans without approval. 5) An ERV & HRV would actual hurt my HERS rating as compared to an exhaust only system and I nned to stay below a 50
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jonr
Senior Member
Posts:5341
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| 22 Apr 2011 04:45 PM |
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When running, Rosalinda's system will cause the house to run at negative pressure and this will pull air through the walls. But this is common and is usually only a problem if the outside walls are wet or the AC is on.
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schlick
New Member
Posts:6
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| 22 Apr 2011 04:54 PM |
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What is a Rosalinda's system? I wouldnt want to be pulling moisture into my walls and cause mold. The exhuast fan will be runing 24hr/day |
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Rosalinda
Basic Member
Posts:353
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| 22 Apr 2011 11:38 PM |
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jeffs, my system is described in my post above, I have a range vent and a bathroom vent in the main living area (we have an open plan), and the Panasonic vent fan in the ground floor (also open plan). Fresh air (make up air) is provided by windows, as long as the weather is good, and by the solar air box with its 4 inch opening to the outside during the coldest months. I guess Jonr does not think the 4 inch opening is big enough to provide sufficient makeup air in the winter, resulting in negative pressure in the house - so I may have to crack open a window also if this becomes the case.
I do also use a dehumidifier in the house as needed, though understand the problem with pulling air in through the walls - not a good thing, and indeed rather difficult given the, 1.4 ACH50 the house evaluated at, so I will have to be cognisant of negative pressure, and take remedial measures as needed.
No AC in my house - not needed in this area.
-Rosalinda |
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| Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified |
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jonr
Senior Member
Posts:5341
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| 23 Apr 2011 08:12 AM |
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Correct - for example, a 4" duct without a fan (intake) is no match for a 4" duct with a fan (exhaust). It is unbalanced and will create pressure. On the other hand, a 4" fan blowing in and another 4" fan blowing out will be fairly well balanced (and can easily be adjusted to get exactly neutral house pressure).
But with dryer vents, bathroom fans, gas hot water heaters, closed supply ducts, furnaces and under slab radon fans, negative house pressure is quite common.
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Rosalinda
Basic Member
Posts:353
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| 23 Apr 2011 02:23 PM |
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Thanks Jonr, maybe I will add a fan to the box if there is negative pressure - as always appreciate the great info you provide.
-Rosalinda |
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| Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified |
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Sporto
New Member
Posts:18
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| 23 Apr 2011 03:45 PM |
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Great topic. I'm building a house with radiant floor heating throughout. Like Jeffs, the only planned venting were bathroom and laundry vents. I've installed qty 6 90 CFM Panasonic programmable fans in bathrooms and laundry spaces for venting but after reading up became concerned about creating negative pressure condition while not allowing any fresh air ingress. In response, I am currently planning on installing 2 195 CFM HRV systems by Lifebreath in the house to try and neutralize the pressure while also allowing for fresh air circulation in house.
Any input or thoughts are much appreciated as we're at the point in the building where we can effect the outcome if there are tweaks to the system above that need to be made.
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jonr
Senior Member
Posts:5341
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| 23 Apr 2011 09:54 PM |
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I'd like to see more effort put into identifying ways to reduce ventilation needs - ie, what is causing the humidity, smells or offgassing that causes the need to ventilate so much.
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Sporto
New Member
Posts:18
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| 23 Apr 2011 10:37 PM |
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I was under the impression that getting some amount of fresh air exchange in the house for recirculation was a good thing. I believe the bathroom fans are to exhaust humidity and odors. The HRV's are to get some fresh air circulation. Am I missing something?
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Rosalinda
Basic Member
Posts:353
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| 24 Apr 2011 12:03 AM |
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The problem with HRVs is that they require ductwork. I want the absolute minimum of duct work in my house, to prevent the dust and stuff that accumulates in ducts and blows around, and I imagine there are many folks who install radiant systems as a way of getting away from ductwork. The only ductwork I have runs the few feet from the vent fans to the outside. BUT, you still need a way to bring in fresh air to balance the not so fresh air vented out.
This is easy to do in warmer weather with windows, but more challenging in the cold winter months.
-Rosalinda |
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| Sum total of my experience - Designed, GCed and built my own home, hybrid - stick built & modular on FPSF. 2798 ft2 2 story, propane fired condensing HWH DIY designed and installed radiant heat in GF. $71.20/ft2 completely furnished and finished, 5Star plus eStar rated and NAHB Gold certified |
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jonr
Senior Member
Posts:5341
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| 24 Apr 2011 10:06 AM |
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I understand ventilation under some conditions - cooking on the stove, bathroom is in use, wet dogs came inside, etc. But why can't we get by with less than spec during normal conditions? If an answer is "off gassing from the carpet is bad for you", then maybe less toxic carpet should be used. If excess humidity is an issue, then let's look at where it is coming from. |
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acwizard
Basic Member
Posts:265
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| 24 Apr 2011 03:32 PM |
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ASHRAE has done extensive research on minimum ventilation rates. Without reaching these values , one is subjecting occupants to chemicals and other pollutants which have been proven unhealthy. |
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jonr
Senior Member
Posts:5341
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| 24 Apr 2011 04:24 PM |
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I'm sure this finding is highly situation dependent. Some buildings are all concrete and steel - unlikely there is much chemicals/pollutants involved there.
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Sporto
New Member
Posts:18
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| 24 Apr 2011 09:33 PM |
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Are these commercially available or are they custom built?
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