Resolved my Humidity problem !!

[BIGSHOT]

I was Lucky to get my hands on an Air Exchanger for my garage..
I have a radiant floor and when I came in with all the snow or washing the car the Humidity would go to 60-70% ... My garage is built very tight.

I know a lot of people will say it's overkill but I got it for free ...

 

[ambenz]

Is this air handlier have a built in dehumidifier?
How does it process humid air?
Sure looks like a humidity stat for what I use on my furnace to humidify my home in the winter using a humidifier.
And how in the heck do you score a free air handlier? ....there gonna be a few "you" Su*&^!" flying around, for sure!

 

[BIGSHOT]

This is an Air exchanger. It takes the Old air Inside ( humid ) and replaces it with Fresh new air from Outside ( Dry air ) . It has heat recovery so the air that is brought from Outside is warmed up before. If the air is really humid Inside there's a drain on the bottow. I also think the drain is for a de-icing cycle.

I'm not an expert by any means but Here in Québec every house has one now it's a law.
Houses are built too tight.

 

[DC73]

There are two types of these devices. One is an HRV (heat recovery ventilator) and the other is an ERV (energy recovery ventilator).

An HRV works by replacing stale indoor air with fresh outdoor air. These are installed in tight homes to get adequate ventilation into the home and are sometimes installed with their own duct system. The design of the device allows a transfer of heat from one airstream to the other in order to temper the incoming air. They can also control humidity to some extent like in the OP's situation where the garage is more humid than the outdoor air. There are other less expensive ways to accomplish ventilation in a tight house.

An ERV does the same thing as an HRV but is also designed to transfer moisture from whichever air stream is the most humid to whichever is the most dry. This helps to maintain correct indoor humidity levels as in the winter, the more humid outgoing air can give up some of its humidity to the incoming dry air and in the summer, the humid incoming outdoor air gives up some of its humidity to the drier outgoing air.

Nice score!

DC

 

[BIGSHOT]

Well this is a HRV then ! Good explanation DC73. At zero $ it made sense. I understand theres others way of doing it that cost much less ...

 

[yeldogt]

Having had both -- the filters are expensive and the ERV's can freeze in a cold climate

ERV's were introduced to remove moisture from the outside air before being introduced into a building. They use inside conditioned air from the building to both temper the outside air and to remove some of the moisture. They were developed for hot climates where the needed outside fresh air was at a higher humidity.

The only way they can reduce humidity inside a building is if the outside air is at lower humidity level ... they work at about 70 percent max efficiencies not including the fan.

In my last couple of builds I ditched the recovery ventilators.

I use a system that incorporates a dehumidifier. When the inside air is too humid or the exterior incoming air is .. the unit will remove the humidity. The rest of the time I have a small fan that is introducing air in a timed fashion. In many building Recovery Ventilators are too big and waste energy.

 

[BIGSHOT]

Well this system cannot freeze ... And this HRV filter are metal and easy to wash.

In the climate I'm in that's what works. If I was in Florida it may not be a good solution.

 

[yeldogt]

Well this system cannot freeze ... And this HRV filter are metal and easy to wash.

In the climate I'm in that's what works. If I was in Florida it may not be a good solution.

They normally have a set of metal and a set of replaceable and if it is cold enough and humid enough at the same time they will freeze -- many have heaters or the fans reverse.

You will have to see how much the unit needs to run understanding that is is wasting up to 40% of the conditioned air ..

In my case using propane in the winter the RV wasted too much - using a system that only replaced the air needed to freshen the space was better for me

 

[MTMH80]

I have the same clock in my garage. Nice.


Sent from my iPhone using Tapatalk

 

[pseudorealityx]

Having had both -- the filters are expensive and the ERV's can freeze in a cold climate

ERV's were introduced to remove moisture from the outside air before being introduced into a building. They use inside conditioned air from the building to both temper the outside air and to remove some of the moisture. They were developed for hot climates where the needed outside fresh air was at a higher humidity.

The only way they can reduce humidity inside a building is if the outside air is at lower humidity level ... they work at about 70 percent max efficiencies not including the fan.

In my last couple of builds I ditched the recovery ventilators.

I use a system that incorporates a dehumidifier. When the inside air is too humid or the exterior incoming air is .. the unit will remove the humidity. The rest of the time I have a small fan that is introducing air in a timed fashion. In many building Recovery Ventilators are too big and waste energy.

ERV's are designed around the code required outside air requirements, or the exhaust requirements, whichever is larger. To say they are 'too big' as a blanket statement is not looking at the whole picture, or not understanding how/why they're sized the way they are for the application.

Dehumidifiers have limitations, and waste energy as they dump all the energy of the cycle right back into the building. And 'real' dehumidifiers (desiccant) cost BIG money.

 

[yeldogt]

ERV's are designed around the code required outside air requirements, or the exhaust requirements, whichever is larger. To say they are 'too big' as a blanket statement is not looking at the whole picture, or not understanding how/why they're sized the way they are for the application.

Dehumidifiers have limitations, and waste energy as they dump all the energy of the cycle right back into the building. And 'real' dehumidifiers (desiccant) cost BIG money.

Since the OP mentioned tight building and humidity, I'm assuming he is not using the RV as an exhaust fan. They are not used for "make up air" for exhaust fans (bath/ stove)

I live in the mid-atlantic and with most areas of the country with green grass -- we have high enough humidity part of the year to cause problems in a tight house. Having a proper whole house dehumidifier incorporated into the system eliminates the humidity problem when the outside air is too humid to reduce interior humidity.

In my experience with the average household number and square footage the RV's don't have to run very long before the air change is greater then needed. RV can waste a lot of energy with too much air change. I would rather do a much smaller fan, tailored to the needed load, so that the air is being introduced over a longer time. This also provides the additional benefit of slightly pressurizing the house -- this helps against the stack effect. Very important in radon areas as it can eliminate the need for continues fans under the slab.

My point in responding is that RV's are not really about reducing interior humidity .. and may don't understand the limitations or cost.

I use the smallest Santa Fe in my shop with two inputs - one outside and one from the interior with a controller.

 

[pseudorealityx]

Since the OP mentioned tight building and humidity, I'm assuming he is not using the RV as an exhaust fan. They are not used for "make up air" for exhaust fans (bath/ stove)

They can be in commercial applications, or a small one could be even in a residence to also pressurize at the same time.

I live in the mid-atlantic and with most areas of the country with green grass -- we have high enough humidity part of the year to cause problems in a tight house. Having a proper whole house dehumidifier incorporated into the system eliminates the humidity problem when the outside air is too humid to reduce interior humidity.

And they also dump heat into the air stream and they're limited to a certain dew point based on their design.

In my experience with the average household number and square footage the RV's don't have to run very long before the air change is greater then needed. RV can waste a lot of energy with too much air change. I would rather do a much smaller fan, tailored to the needed load, so that the air is being introduced over a longer time. This also provides the additional benefit of slightly pressurizing the house -- this helps against the stack effect. Very important in radon areas as it can eliminate the need for continues fans under the slab.

Can't disagree with any of this. Although an ERV should typically be setup to slightly pressurize your space (~10% more supply than exhaust).

My point in responding is that RV's are not really about reducing interior humidity .. and may don't understand the limitations or cost.

That's exactly what they're for. Why else would you use an energy recovery ventilator instead of a sensible only ventilator?

 

[JCByrd24]

The only way they can reduce humidity inside a building is if the outside air is at lower humidity level ... they work at about 70 percent max efficiencies not including the fan.

This is why the OPs use of the HRV is so effective. Outside air in Canada in winter is almost always incredibly low relative humidity. He can both bring in super dry outside air while exhausting humid air inside without wasting precious heat. 70% efficiency at this transfer is tons better than opening a window and running an exhaust fan. Interiors of tight houses in cold climates need the same treatment due to moisture from cooking and bathing, again it works very well and clean breathing air is critical side effect that means it makes more sense than a dehumidifier, again in tight houses. Leaky houses up here don't need either but aren't efficient. Running and HRV 24/7 I would agree is probably overkill and a waste of energy.

Comparing either of those to the summer in the mid-atlantic isn't really applicable. Assuming you still want breathing air you need some strategy. Simply opening windows is one, but if you don't o that you can choose a method that recovers some of your interior conditioning or not. As you said an ERV won't dry the air in either case, it will only help not waste the conditioning you've done inside, be it cooling (which usually has dehumidification built in) or dehumidification only.

My only thought for the OP would be to separate the supply and exhaust ducting a little further to avoid any short cycling between the ducts.

 

[BIGSHOT]

Right on JC ... Here in quebec the outside air is dry in winter. We turn the HRV off during summer. I had the same concern about the supply/exhaust. I did some testing and it works great that way.

 

[ambenz]

Very cool explanations everyone.
I have a semi-tight house with good windows and doors.
I smoke in the house and I would like to use one of these units to replace the air in the house.
I am gonna look into these more.
I have seen modules of ERV in big air handling units and they seemed like dust collectors more than recovery units...and wondered how well they worked.
Guess I'll be re-examing my thoughts on these units.

 

[yeldogt]

You guys need to do a bit more reading -- and understand the costs of both purchasing and running these things . 70% is the max and it does not include the fan. 60% is more realistic -- that is 40% wasted.

And yes .. in the winter with dry outside air the HRV will reduce interior humidity ... They do nothing in the summer if you have humid outside air .. and you will still have the inside humidity .. actually greater then in the winter.

ERV -- are designed to reduce the humidity of the incoming air -- they do nothing to reduce the interior humidity unless this air stream is a lower level . and this will not be the case in the summer in humid climates (green grass). A tight house will always need some humidity control.

They work great for smokers -- efficiencies are irrelevant -- getting the smoke out os the point.

 

[yeldogt]

Right on JC ... Here in quebec the outside air is dry in winter. We turn the HRV off during summer. I had the same concern about the supply/exhaust. I did some testing and it works great that way.

So what do you do in the summer?

 

[yeldogt]

That's exactly what they're for. Why else would you use an energy recovery ventilator instead of a sensible only ventilator?

In many parts of the world the exterior moisture level is too high to use untreated air for ventilation .. EVR use the expensive conditioned air to reduce the incoming humid air so that the moisture contained in the fresh air is reduced and does not need to be removed through expensive AC.

It is less efficient -- around 50% .. but cheaper then using refrigerant on a larger scale.

If you live in an area close to 50% -- an efficient dehumidifier and fresh air intake are better .. simple filters and efficient transfer.

 

[BIGSHOT]

Yeldogt i live in Quebec not somewhere in Ireland ... 1- this is a garage not a house. 2- i got this unit for FREE. 3- here in Quebec the new building codes requires an HRV based on the air being more poluted in the house then outside because houses are built very tight. 4- in the summer it's turned off. Some people have A/C in their house and some open the windows. It's not humid here in the summer like it would be in Florida let's say. 5 - Electricity here cost way less then then anywhere in North America. 6- I set it to 45 percent humidity and it only start when humidity gets above this . Theres also a setting where i could leave the HRV always on at low speed and kicks in high speed after but i dont need this in mu Garage.

Hope you understand more about my location/application/price paid for this setup

 

[yeldogt]

Bigshot: I understand -- I pointed this out in my post #11. I'm not attacking your installation.

We require air exchanges also -- I was only pointing out that HRV's and ERV's are not the only way to go and often are not the best. And that 60- 70 % can still be wastefu.

Many people think they reduce humidity -- they don't. They move air ... if the outside air is lower humidity they will move that dryer air inside.

Buildings still need fresh air at times of the year when A/C may not be needed and the humidity is high.

These things get great marketing -- thankfully I have read some articles recently explaining the deficiencies.

They have a place --

 

[jvitez]

Great score Bigsot! That's an excellent setup for your needs and climate.

I might suggest you do something with the ducting though, as the intake and exhaust are pretty close together, so might get the fresh outside air being sucked into the intake pipe. Perhaps run some galvanized duct up the wall to the peak for discharge air, and run the intake down closer to the floor when the melting snow would be. Or your could run each horizontally across the wall on opposite sides. Just a thought.

I have two HRV's in my house, and we never have a humidity problem nor musty smells.

 

[JCByrd24]

So what do you do in the summer?

In the summer in Maine and Canada we open windows most of the time. I use window AC at night when it's hot and humid in July/August.

I'm not getting what you are suggesting people do for breathing air other than open a window that would use less energy than an ERV/HRV. In your climate you clearly need AC/dehumidification to keep in comfortable inside. If you than do a non-recovery air exchange you are at 0% efficiency (run the AC with the windows open), so 60-70% is better.

The point we are making to you is that in our climate in the winter they do both (air exchange and dehumidify) for less energy that a separate air and dehumidification scheme. Dehumidifiers use way more electricity than and HRV due to the compressor vs a fan. Then you still need fresh air.

 

[pseudorealityx]

In many parts of the world the exterior moisture level is too high to use untreated air for ventilation .. EVR use the expensive conditioned air to reduce the incoming humid air so that the moisture contained in the fresh air is reduced and does not need to be removed through expensive AC.

It is less efficient -- around 50% .. but cheaper then using refrigerant on a larger scale.

If you live in an area close to 50% -- an efficient dehumidifier and fresh air intake are better .. simple filters and efficient transfer.

Again, commercial world here...(and please notice my location before you imply I don't understand elevated humidity levels) Even in high humidity climates, normal DX HVAC equipment can handle 15-20% untreated outside air and maintain acceptable humidity levels. Beyond that and you have to check your calculations.

But the key here is that in the commercial world, the amount of ventilation air is a code requirement, so you can only adjust it so much while maintaining code compliance.

In high occupancy spaces, you typically have larger restrooms, break rooms, janitor closets, electrical rooms, etc that all require exhaust anyway, so it's efficient to bring those to a centralized ERV to offset the heat (both sensible and latent) from the ventilation air. Using that strategy, you can increase the % of outside air going to your standard HVAC units.

Also, a good ERV can be 70+% efficient. I typically specify them running ~10% more supply air than exhaust air, which reduces the efficiency a few points, but also takes care of pressurization. I'm guessing you're more familiar with the plate style HRV's and ERV's, as those have MUCH higher static pressure requirements on the air side. So much so that when you run an energy model simulation, even adding a 3rd motor to turn a desiccant wheel is better. I won't specify a plate style if I can help it.

Also, going back to dehumidifiers... residential style units are just DX refrigerant systems with the condenser section in the same airstream. All of the fan heat, and all of the compressor heat goes directly into your air steam and into your space. Typically not the solution you want in the summer months.

 

[Radix2]

With all this talk of dehumidifiers in cold climates during the cold season - the op has a special case with his large and frequent evaporation of melt water?

The common experience I have requires forced humidification in the winter - is this simply a matter of not having experience with really tight construction? It would seem more than that to me, and also imply a high level of moisture producing activity - I.e. Would the normal activity of a couple people generate enough moisture to require dehumidification in a 2000sqft tight house in winter ? Are these tight houses installing humidifiers as well as the HRVs in case insufficient waste moisture is generated? ( you might come home from a vacation and find your woodwork a bit "gappy" from the 5% humidity...)

The worst air humidity condition has to be the cool damp months when a/c is not available to dehumidify, and the slightly heated outside air is still far too damp - is there a better way to handle this than a dehumidifier ?

 

[pseudorealityx]

Worst humidity conditions as far as indoor comfort are warm days right after rain. That's when you've got an outside temperature very close to your indoor temperature (so little need for cooling), but very high dew points, 90+% RH. This is called the design dehumification. Here in the Atlanta area, it's about 81 degrees dry bulb, with a 76 degree wet bulb.

Depending on your definition of cool, even if the relative humidity is 100%, once you warm it up to normal indoor temperatures (~70 or so), the RH comes down to normal levels.

 

[JCByrd24]

Radix, you have a house like mine, in a similar climate: normal to leaky, not tight. It takes a pretty good amount of care and intent to build a tight enough house to have high humidity problems in winter in cold climates. But once you do, it happens and all winter long and seriously. Everyday activities of bathing, cooking, and breathing all create a lot of moisture that need attention. My house is average construction and does not NEED any humidification or dehumidification really. Some days a humidifier would be nice; super cold days I get a little condensation on the windows, mostly from cheap windows though. My bath fans are on a timer and run at least an hour per shower. My boiler does air exchange, it is not a fancy one with outside air direct to it.

For us in the north I concur on your assessment of the uncomfortable humidity day. Those cool shoulder season days seem worse/colder than a dry actually cold day. The best way in my mind to deal with this is crank the heat. Heating air lowers it's relative humidity and makes it warmer, a win win. This is why your house feels so dry in winter, you're heating air that already has a very low relative humidity.

pseudo, your situation was my own answer to the question I posted to yeldogt. I was neglecting to consider that in the south ducted air systems likely already include dehumidification and in those cases it likely makes sense to mix in a little outside air with that system than install a whole other system with ducting and motors etc. I'm very unfamiliar with commercial apps other than I know they require a lot of ventilation, so as they get larger and larger I'm sure it makes better sense to add energy recovery.

 

[DEnd]

Yeldogt i live in Quebec not somewhere in Ireland ... 1- this is a garage not a house. 2- i got this unit for FREE. 3- here in Quebec the new building codes requires an HRV based on the air being more poluted in the house then outside because houses are built very tight.

Indoor air isn't more polluted than outside air because the houses are too tight. Even in highly leaky houses air pollution can easily be greater indoors than outdoors. This is because a leaky house does not guarantee air exchange, and the air exchange that does happen isn't source controlled.

Running the air exchanger at 10% over does help with some of the symptoms of the stack effect, but it doesn't eliminate it. It does help control the source of incoming air, but you are still moving warm moist air out of the building envelope at the top. Likewise depressurizing the house can stop the warm moist air moving out through the top of the house, but it doesn't control the source of incoming air.

A balanced system can be designed to handle both. You will still get some air leakage into the house uncontrolled so a radon mitigation system will need to be installed if radon is a problem in the area, and likewise some air leakage will still occur so the wall and roof need to be built to handle that. However, the majority of the what causes the problems is taken care of by a well designed balanced system.

 

[yeldogt]

The OP spoke of a tight building. Some are saying "leaky" .. he said it was "tight".

I have built many tight buildings. I'm only talking about tight buildings. They will have issues from time to time in the winter with heat and no additional ventilation with normal family activity. In the humid summer with AC running correctly -- they usually have no humidity problems. What happens on those shoulder days in the late fall and early spring when the outside humidity is too high? That's when they have problems.

The OP talked about "washing cars" and "snow". In a tight building -- where is this going to go? He has ventilation ... great. My thought was ... how long does the ventilator need to run to bring down the level? They can waste a lot of conditioned air. That is all I was pointing out.

Commercial requirements are completely different.

My experience: In the shoulder seasons when no heat or AC is running to condition the inside air --- interior humidity can be a problem. It is also humid in many parts of world at that same moment. Simple ventilation will not work .. I am talking tight buildings. Factor in bath/ kitchen fans .. and in my area Radon fans .. they need more than a RV.

So what do you do when ventilation will not work? The easiest solution is to add a dehumidifier to the system -- for those periods.

I was only trying to make the point that the ventilators are not always solutions. Many people put them in tight houses not understanding what they do and what they cost in lost energy (conditioned air).

Modern whole house dehumidifiers - are very efficient. Setup properly they work well and eliminate humidity automatically. Mine almost never run in the summer -- so waste heat is not an issue. Having something working when needed is cheaper then running a 200cfm fan when a 60 cfm fan pressurizing the building would be better.

I do exactly what the OP does in my studio/ garage and control it all using a whole house dehumidifier.


I'm not attacking the OP's setup ,, just pointing some things out.

 

[BIGSHOT]

The OP talked about "washing cars" and "snow". In a tight building -- where is this going to go?

I have a drain and what I do now is try and squeege the water to it when I wash my car or bring in my snow blower.