HRVs/Filtration

[LegendKiller]

I have a new house in MN but I have some cold spots. The builder put in always-on fans rather than powered ventilation (HRV/ERV) and I am wondering if it makes more sense to put in a powered system. Anybody have experience with these? Do they help?

 

[Scarpozzi]

I googled what HRV/ERV is... That's how little I know about it.

But...logic says that cold spots are a sign of issues that may be solved through adjustments in system pressure or vent size changes...or insulation adjustments. I've got a few rooms in my house that have windows and definitely have air leaks...plus have smaller than average vents. This causes them to feel cold (all are bathrooms), so they tend to get additional cold air through exhaust vents and pipe corridors.

You may want to consider searching for possible air leaks and possibly changing the kind of diffuser you have in that room to make sure you're getting the most pressure possible from your system. Sheetrock work can be nasty, but sealing the walls can make a HUGE difference. Especially if you can locate air leaks in the wall and seal them up with foam insulation.

HRV may help, but it appears to be more of a 'green technology' that may not help much. Air circulation in the winter can be a double edged sword. It helps circulate humidity, which can help make the place feel warmer, but can also spread cold air if your furnace isn't running at the time....which is worse. If the vents are too far from the heat source, they can also lose enough temp that they always blow cool air rather than warm air.

Finally, remember space heaters aren't so bad in those cold rooms....especially if you don't use them often. Just be safe with them.

 

[Booty]

What do you mean always on fan? Like the furnace (air handler) blower is always running? Do you have a fresh air intake for ventilation of some sort?

Where are the cold spots? Are you getting drafts from doors and windows? Are there exterior walls that feel cold (poor insulation)? Are some rooms just colder than others (unbalanced system)?

I would think an HRV/ERV would be more for a scenario where the whole house is cold and having trouble keeping the air warm that's coming in for ventilation. I think they're more common when homes are "tight" - the trend towards eliminating air leaks and making houses more efficient also eliminated natural sources of fresh air/ventilation, so it introduced the need for mechanical ventilation. Do you have outside air being introduced into your central forced air system?

 

[LegendKiller]

What do you mean always on fan? Like the furnace (air handler) blower is always running? Do you have a fresh air intake for ventilation of some sort?

Where are the cold spots? Are you getting drafts from doors and windows? Are there exterior walls that feel cold (poor insulation)? Are some rooms just colder than others (unbalanced system)?

I would think an HRV/ERV would be more for a scenario where the whole house is cold and having trouble keeping the air warm that's coming in for ventilation. I think they're more common when homes are "tight" - the trend towards eliminating air leaks and making houses more efficient also eliminated natural sources of fresh air/ventilation, so it introduced the need for mechanical ventilation. Do you have outside air being introduced into your central forced air system?

Our non-ECM furnace blower is always running to try to event out the temps. We have a F/A intake in the basement, just a big insulated flex pipe coming in near the furnace.

I am having the gas company out to do an energy audit with a IR gun to see if there are windows with abnormal drafts, if so, I am going back to the builder. Also having an AC guy come out to balance it, the builder guys supposedly did it but I think they did a crap job.

We have a big enough furnace but might have more insulation blown in.

 

[LegendKiller]

We had an HVAC guy in - he pretty much said there wasn't much to do. We could go the AeroSeal route at ~2.5k or Arzel multi-zoning for ~4-5k. A cheaper alternative a friend of mine mentioned was the Honeywell Prestige thermostat which would allow multi-zone temp sensing and keep the furnace on longer with the colder rooms.

We are having an energy auditor out next week to see if theres any problems with the windows in those rooms, check insulation...etc. We'll see what he says.

If there's something wrong with the house the builder is going to find out what happens when you try to pull a fast one.

 

[Booty]

We had an HVAC guy in - he pretty much said there wasn't much to do. We could go the AeroSeal route at ~2.5k or Arzel multi-zoning for ~4-5k. A cheaper alternative a friend of mine mentioned was the Honeywell Prestige thermostat which would allow multi-zone temp sensing and keep the furnace on longer with the colder rooms.

We are having an energy auditor out next week to see if theres any problems with the windows in those rooms, check insulation...etc. We'll see what he says.

If there's something wrong with the house the builder is going to find out what happens when you try to pull a fast one.

I had to Google AeroSeal. That could probably be helpful in overall performance, but wouldn't really do much for an imbalance unless the cold rooms happened to have the most ductwork leakage. Are the joints in the ductwork sealed and taped? If it's a new house I'd expect that to be done - so if you have leaky ductwork I'd definitely be upset with the builder and try to get them to foot the bill to remedy, whatever the solution is. No excuse for leaky ductwork in new construction these days.

If you can't even out temperatures in all spots/rooms through manually adjusting the registers and dampers in the ductwork you could look into retro-fitting a zoning system with automated dampers and multiple thermostats. The benefit there would be you could also heat/cool certain rooms more than others, so it's more flexible/customizable. How practical or expensive it would be to implement would depend on the house's layout. For example, I've considered converting two a 2-zone system as our ductwork T's off above the furnace going left to all the bedroom and to the right for the rest of the house, which is pretty ideal.

Funny you mention the Prestige system as I've been looking at it recently. I actually just put in Honeywell's Wi-Fi Smart Thermostat and am pretty happy with it. I'm not sure if I can actually build off it or not if I want to incorporate their zoning or accessory controls, but I didn't want to invest in the whole solution yet as we may be doing some major renovation that involves reconfiguring ductwork anyway.

Anyway - regarding the thermostat - it's great and all to read temps from multiple rooms, but without setting up separate zones really all you're doing is setting a minimum temperature - so if the bedroom is 68 when the house is 72 but they're not separate zones, to get the bedroom to 72 you might bring the rest of the house up to 75-76. So it's really just effectively the same as setting your thermostat higher, I think. I think the Ecobee3 thermostat does this as well... or maybe it takes an average of all the readings...

In regards to the fan used for circulation/evening the heat, our old cheap-o thermostat had 2 fan settings - "on" or "auto". "On" would run the fan non-stop (sounds like your setup), "auto" kicked in on only when the furnace (or A/C) ran. The Honeywell has a "circulate" option which runs the fan sporadically through the day... like 1/3 of the time I think is what the manual said. Enough to provide a little more evenness, but not so costly as running the thing non-stop. Haven't used that feature yet, but I've only had this t-stat a few days.

The energy audit will help for sure... you can also do smoke/feather tests near your windows and doors to check for drafts, or if you can get your hands on a temperature gun you can go around looking for cold spots in walls, etc. If you're adventurous you could carefully pull back a couple trim pieces around windows and doors to see if the space between the jambs was insulated - again, these days it should have low-expansion foam filling the gap, but lazy/old methods involved stuffing newspaper of fiberglass in, if anything.

Another thing to check would be how your rim joists are insulated. Check the article on Fine Homebuilding's website - "Insulating Rim Joists". Again, that's more of an overall efficiency thing rather than your ductwork being balanced, but it may give you an idea of whether your builder took shortcuts.

 

[LegendKiller]

I had to Google AeroSeal. That could probably be helpful in overall performance, but wouldn't really do much for an imbalance unless the cold rooms happened to have the most ductwork leakage. Are the joints in the ductwork sealed and taped? If it's a new house I'd expect that to be done - so if you have leaky ductwork I'd definitely be upset with the builder and try to get them to foot the bill to remedy, whatever the solution is. No excuse for leaky ductwork in new construction these days.

If you can't even out temperatures in all spots/rooms through manually adjusting the registers and dampers in the ductwork you could look into retro-fitting a zoning system with automated dampers and multiple thermostats. The benefit there would be you could also heat/cool certain rooms more than others, so it's more flexible/customizable. How practical or expensive it would be to implement would depend on the house's layout. For example, I've considered converting two a 2-zone system as our ductwork T's off above the furnace going left to all the bedroom and to the right for the rest of the house, which is pretty ideal.

Funny you mention the Prestige system as I've been looking at it recently. I actually just put in Honeywell's Wi-Fi Smart Thermostat and am pretty happy with it. I'm not sure if I can actually build off it or not if I want to incorporate their zoning or accessory controls, but I didn't want to invest in the whole solution yet as we may be doing some major renovation that involves reconfiguring ductwork anyway.

Anyway - regarding the thermostat - it's great and all to read temps from multiple rooms, but without setting up separate zones really all you're doing is setting a minimum temperature - so if the bedroom is 68 when the house is 72 but they're not separate zones, to get the bedroom to 72 you might bring the rest of the house up to 75-76. So it's really just effectively the same as setting your thermostat higher, I think. I think the Ecobee3 thermostat does this as well... or maybe it takes an average of all the readings...

In regards to the fan used for circulation/evening the heat, our old cheap-o thermostat had 2 fan settings - "on" or "auto". "On" would run the fan non-stop (sounds like your setup), "auto" kicked in on only when the furnace (or A/C) ran. The Honeywell has a "circulate" option which runs the fan sporadically through the day... like 1/3 of the time I think is what the manual said. Enough to provide a little more evenness, but not so costly as running the thing non-stop. Haven't used that feature yet, but I've only had this t-stat a few days.

The energy audit will help for sure... you can also do smoke/feather tests near your windows and doors to check for drafts, or if you can get your hands on a temperature gun you can go around looking for cold spots in walls, etc. If you're adventurous you could carefully pull back a couple trim pieces around windows and doors to see if the space between the jambs was insulated - again, these days it should have low-expansion foam filling the gap, but lazy/old methods involved stuffing newspaper of fiberglass in, if anything.

Another thing to check would be how your rim joists are insulated. Check the article on Fine Homebuilding's website - "Insulating Rim Joists". Again, that's more of an overall efficiency thing rather than your ductwork being balanced, but it may give you an idea of whether your builder took shortcuts.

As with most homes the builder only really did the code minimum, so they didn't tape ductwork. This isn't a cheap home either, just corners cut and our first home, so it's a learning experience. Most people in our development are in the same spot.

I agree on the temp increase, but then I was going to shut down vents in the different rooms that are hotter to try and even things out a bit.

Our thermostat (Trane z-wave) only has auto/on, so the honeywell may be a little better there.

One of the neighbors retrofitted their house with 4 zones for $10k (incl. system and fixing knock-down). We're not willing to spend that much. I looked at this...

http://www.thisoldhouse.com/toh/video/0,,20810706,00.html

Interesting approach, just not sure on longevity (sharp edges, duct screws, duct cleaning...etc). Also a friend of mine brought up the issue of having too much pressure if too many zones are shut down, burning out the motor.

We might end up insulating the attic better (r-46 now).


Really hoping the home energy audit with IR camera shows some damning evidence. Most HVAC guys in this area build for the big national builders (incl. ours) and don't want to start stuff with them lest they lose out on huge contracts.

 

[iwajabitw]

Before the audit, take a IR thermometer and walk around the room and find those cold spots, then check insulation. I see a lot of tier ceilings that are uneven insulated and sometimes the exterior sides near the soffit, there is very little.

If you close registers you may increase the static pressure on the blower. The HVAC tech should have taken an anemometer and checked the cfms at the registers and return and adjusted based on readings. Also he should have checked static pressure on the blower/furnace. Having blower always running just isn't right, if the ducts are in the attic, there going to cool down when the heat isn't on and blow that into the rooms. In summer when the AC turns off, all of that moisture on the coil is gonna get blown right back into the rooms, so no dehumidification. In AL R-38 is code minimum for insulation, I don't know about MN but I thought it would be 50+. Also check around all of the window on the exterior, Fill any gaps, except weeps, the slits at the bottom, with at least GE 100% Clear Silicone.

 

[LegendKiller]

Before the audit, take a IR thermometer and walk around the room and find those cold spots, then check insulation. I see a lot of tier ceilings that are uneven insulated and sometimes the exterior sides near the soffit, there is very little.

If you close registers you may increase the static pressure on the blower. The HVAC tech should have taken an anemometer and checked the cfms at the registers and return and adjusted based on readings. Also he should have checked static pressure on the blower/furnace. Having blower always running just isn't right, if the ducts are in the attic, there going to cool down when the heat isn't on and blow that into the rooms. In summer when the AC turns off, all of that moisture on the coil is gonna get blown right back into the rooms, so no dehumidification. In AL R-38 is code minimum for insulation, I don't know about MN but I thought it would be 50+. Also check around all of the window on the exterior, Fill any gaps, except weeps, the slits at the bottom, with at least GE 100% Clear Silicone.

The kid that was out did some CFM readings but overall didn't do shit, only checked at the registers and such. I didn't find out till afterwards that his company is another contractor for the builder... I might talk to the other guy from the company and see if he can do something more for me.

If not, I might try to find somebody else. The energy auditor is from the power company so I am hoping I get a little more of a honest answer.

As far as I can tell, R-46 is the minimum here, I am a bit surprised, but that's the area. I'm not sure if they went around and did the caulking or not. Anything I should pay attention to in particular?

Another thing I noticed is a small draft coming through our basement outlets. Not sure whats up there.

This house wasn't cheap...

 

[Booty]

As with most homes the builder only really did the code minimum, so they didn't tape ductwork. This isn't a cheap home either, just corners cut and our first home, so it's a learning experience. Most people in our development are in the same spot.

I agree on the temp increase, but then I was going to shut down vents in the different rooms that are hotter to try and even things out a bit.

Our thermostat (Trane z-wave) only has auto/on, so the honeywell may be a little better there.

One of the neighbors retrofitted their house with 4 zones for $10k (incl. system and fixing knock-down). We're not willing to spend that much. I looked at this...

http://www.thisoldhouse.com/toh/video/0,,20810706,00.html

Interesting approach, just not sure on longevity (sharp edges, duct screws, duct cleaning...etc). Also a friend of mine brought up the issue of having too much pressure if too many zones are shut down, burning out the motor.

We might end up insulating the attic better (r-46 now).


Really hoping the home energy audit with IR camera shows some damning evidence. Most HVAC guys in this area build for the big national builders (incl. ours) and don't want to start stuff with them lest they lose out on huge contracts.

I'd try to tape or seal whatever ductwork you can get at. That will just give you a little more control if you end up trying rebalance things. I don't know the most cost effective way to do this - I still have to do it in our house but as I mentioned our current configuration is most likely going to change so I don't want to quite yet.

That solution on TOH is interesting, but it seems like even when the bags are deflated they'd significantly restrict airflow. If you had a multi- or variable-speed fan in your furnace you might not have to worry so much about pressure-related wear and tear on the blower... I would hope the bags only inflate briefly to balance out the rooms and then all stay deflated most of the time.

 

[Booty]

Before the audit, take a IR thermometer and walk around the room and find those cold spots, then check insulation. I see a lot of tier ceilings that are uneven insulated and sometimes the exterior sides near the soffit, there is very little.

If you close registers you may increase the static pressure on the blower. The HVAC tech should have taken an anemometer and checked the cfms at the registers and return and adjusted based on readings. Also he should have checked static pressure on the blower/furnace. Having blower always running just isn't right, if the ducts are in the attic, there going to cool down when the heat isn't on and blow that into the rooms. In summer when the AC turns off, all of that moisture on the coil is gonna get blown right back into the rooms, so no dehumidification. In AL R-38 is code minimum for insulation, I don't know about MN but I thought it would be 50+. Also check around all of the window on the exterior, Fill any gaps, except weeps, the slits at the bottom, with at least GE 100% Clear Silicone.

He's in MN so I'm guessing the furnace and ductwork are in the basement if he has one. Still good points about blowing unheated or unconditioned air around the house.

Best time to use the fan w/o heat or coiling is spring/fall when you want the circulation but the temperature is fine, or to control humidity. I just replaced our central humidifier and it has a "fan" mode that will allow the humidifier to reach desired RH levels even if there's no call for heat. I plan to put in a whole-home dehumidifier this year that would have a similar function.

 

[Booty]

The kid that was out did some CFM readings but overall didn't do shit, only checked at the registers and such. I didn't find out till afterwards that his company is another contractor for the builder... I might talk to the other guy from the company and see if he can do something more for me.

If not, I might try to find somebody else. The energy auditor is from the power company so I am hoping I get a little more of a honest answer.

As far as I can tell, R-46 is the minimum here, I am a bit surprised, but that's the area. I'm not sure if they went around and did the caulking or not. Anything I should pay attention to in particular?

Another thing I noticed is a small draft coming through our basement outlets. Not sure whats up there.

This house wasn't cheap...

Power Co should be about as unbiased as you're going to get. They'll likely do smoke tests to help locate drafty windows and doors. It sounds like a pain but if they find issues there you can carefully pull back the casing (cut the paint/caulk where the trim meets the wall) and do a better job insulating those gaps w/ low-expansion foam. The caulk outside will help with sealing from the elements as well - but the focus is probably more on preventing water infiltration.

The draft coming from the outlet is similar to the gaps between the framing and doors and windows - there's probably either loose or no insulation around the outlets. They make these little foam covers with outlet cut-outs that you can put behind the wall plates - that might help a little. The wall will still be cold in that area but you shouldn't feel a draft anymore. Actually getting some insulation back there would be a little trickier, but it can be done.

 

[LegendKiller]

Power Co should be about as unbiased as you're going to get. They'll likely do smoke tests to help locate drafty windows and doors. It sounds like a pain but if they find issues there you can carefully pull back the casing (cut the paint/caulk where the trim meets the wall) and do a better job insulating those gaps w/ low-expansion foam. The caulk outside will help with sealing from the elements as well - but the focus is probably more on preventing water infiltration.

The draft coming from the outlet is similar to the gaps between the framing and doors and windows - there's probably either loose or no insulation around the outlets. They make these little foam covers with outlet cut-outs that you can put behind the wall plates - that might help a little. The wall will still be cold in that area but you shouldn't feel a draft anymore. Actually getting some insulation back there would be a little trickier, but it can be done.

We've complained about the colder rooms since we bought/built the house so I have a clear email chain back to the beginning about it. Should be covered under warranty and, if they fight me, they know I am more than prepared to back it up legally. I got them to put $6k of drain tile in because they screwed up a little bit of slope so part of my yard was soggy, cleaned it right up. Almost had them replace my entire kitchen granite because a piece of stone discolored (long story). The replacement slab matches well so we aren't going that far, but they know I'm not going to get fucked without a huge fight, so they usually capitulate.

We'll see how the audit goes and the follow-on conversation. If they don't balk, then we'll get them to do it. If they do, I'll have to go the legal route. If that goes nowhere, then I'll see if my brother can help me sealing.

We have some exposed ductwork in the basement. They only taped the plenum and return but not the supply (??????). They foamed the whole joist/foundation joint and put in foam/aluminum backed insulation. I was going to get some Nashua heavier duty tape and do what I can in the basement. I can handle that stuff.