Heating/cooling advice for garage-condo

[nfamus10]

Looking for some outside opinions on how to heat/cool my garage-condo that I am building. I live in central WI, r30 in the walls and r50 in the ceiling with radiant heat in the slab. Would zone the apartment and garage area separately. Any thoughts?

 

[DOPEPICS]

interested in answers to this as well

 

[Ray916MN]

In slab radiant heat is going to be superior for regular use where the temperature is held within a relatively narrow range and/or where you are going to work on or near the floor often. OTOH, if you're going to only use the garage occasionally, forced air is going to be faster to heat or cool.

Assuming the garage is going to be used primarily for parking daily drivers, I'd go for forced air on a separate zone from the living area. In the winter, you really don't want to park your car in a heated garage as it promotes rusting.

 

[pseudorealityx]

You need separate systems (not zones, systems). If you claim that your location doesn't enforce any codes, then my response is you want separate systems (again, not zones, systems).

 

[theoldwizard1]

In slab radiant heat is going to be superior for regular use where the temperature is held within a relatively narrow range and/or where you are going to work on or near the floor often. OTOH, if you're going to only use the garage occasionally, forced air is going to be faster to heat or cool.

I believe you have this backward. Yes, forced air does a better job of "recovery" (a large change in the desired air temp, typical when opening a large door). It will take more time for the residual heat in the slab to re-warm the air, but a large ceiling fan will help.

Assuming the garage is going to be used primarily for parking daily drivers, I'd go for forced air on a separate zone from the living area. In the winter, you really don't want to park your car in a heated garage as it promotes rusting.

I disagree, especially with forced air. FA tends to be very dry and as long as a daily driver is parked inside over night (8-12 hours) it should have sufficient time to dry out. To achieve the same amount of dehumidification with radiant heat would probably require a higher ambient temp (> 70) and/or longer time.

If you plan to use the garage as more of a work shop, there is nothing like radiant heat. If your feet are warm the rest of you feels warm. The optimal heating and cooling would be a mini-split heat pump with an air handler for heating and A/C and heat exchanger for the in floor radiant heat. This require good design and good controls from an experienced installer.

 

[theoldwizard1]

I live in central WI, r30 in the walls and r50 in the ceiling with radiant heat in the slab.

You also want a minimum of 2" of solid foam insulation under the floor. Run the foam board vertically along the inside of the footing to prevent heat loss horizontally.

Would zone the apartment and garage area separately. Any thoughts?

They absolutely need to be separate zone. It may be easier and cheaper to operate is they were totally separate systems.

 

[Ray916MN]

I believe you have this backward. Yes, forced air does a better job of "recovery" (a large change in the desired air temp, typical when opening a large door). It will take more time for the residual heat in the slab to re-warm the air, but a large ceiling fan will help.

It all depends on your holding temperature. If you hold your garage at 40F during the winter, and want to work in it at 64F, forced air will be faster to achieve 64F air temp. My assumption is regular use means higher holding temp, so in slab radiant is preferred. Infrequent use, means lower holding temp, so forced air is preferred because it will get the space up to a comfortable working temp faster.

I disagree, especially with forced air. FA tends to be very dry and as long as a daily driver is parked inside over night (8-12 hours) it should have sufficient time to dry out. To achieve the same amount of dehumidification with radiant heat would probably require a higher ambient temp (> 70) and/or longer time.

First off all heat is essentially dry. The moisture in a heated garage is from the moisture in the air. When you bring a car with snow into a garage, the ice melts and the water evaporates ending up in the air. The air is dry in the winter, because the water drops out of the air as ice. When you melt the ice and snow from your car in the garage you make the air in your garage more humid than it would be if you left it frozen as snow and ice unless you vent the air to the outside.

Whether you succeed in melting all the ice and snow and getting it to evaporate in the air all depends on your holding temperature. If you hold at 40F your garage floor might dry out but more importantly the salt/sand slurry packed into the crevices of your bodywork will definitely not dry out OTOH the air will be moister and it will be warmed and rust will be accelerated (warm moist air with salt is like ocean air). Certainly if your holding temp for your garage was 60F+ your car might dry out completely, but it will be in warmer moister air and for the majority of its time in the garage it will be wet with accelerating rust going on and you will pay for the accelerated rust with a noticeably higher utility bill. In a heated garage used for parking daily drivers and infrequently used to work in, I only use the heat when I need to work in it, otherwise I leave it off so I'm not paying for heat to make my cars rust faster.

 

[pseudorealityx]

First off all heat is essentially dry.

This is wrong. There's 2 kinds of heat in HVAC applications. Sensible and latent. Latent is water content. What you really should be saying is that, "heating typically does not add additional moisture to what you start with".

The moisture in a heated garage is from the moisture in the air.

And any people or infiltration.

When you bring a car with snow into a garage, the ice melts and the water evaporates ending up in the air. The air is dry in the winter, because the water drops out of the air as ice.

No, the air is dry in winter because air cannot physically hold a lot of moisture when it's cold. It has nothing to do with ice.

When you melt the ice and snow from your car in the garage you make the air in your garage more humid than it would be if you left it frozen as snow and ice unless you vent the air to the outside.Whether you succeed in melting all the ice and snow and getting it to evaporate in the air all depends on your holding temperature. If you hold at 40F your garage floor might dry out but more importantly the salt/sand slurry packed into the crevices of your bodywork will definitely not dry out OTOH the air will be moister and it will be warmed and rust will be accelerated (warm moist air with salt is like ocean air). Certainly if your holding temp for your garage was 60F+ your car might dry out completely, but it will be in warmer moister air and for the majority of its time in the garage it will be wet with accelerating rust going on and you will pay for the accelerated rust with a noticeably higher utility bill. In a heated garage used for parking daily drivers and infrequently used to work in, I only use the heat when I need to work in it, otherwise I leave it off so I'm not paying for heat to make my cars rust faster.

Your logic is all wrong. Evaporation doesn't have much to do with it. The temperature determines how much moisture the air can hold. You could turn it up to 110, but ventilate the **** out of it with 20 degree outside air, and you will both dry out every last crevice in the car, and NOT have rusting issues. Rust requires moisture, and if you're sensible heating 20 degree air, you have barely any moisture in the air.

 

[Ray916MN]

....

Your logic is all wrong. Evaporation doesn't have much to do with it. The temperature determines how much moisture the air can hold. You could turn it up to 110, but ventilate the **** out of it with 20 degree outside air, and you will both dry out every last crevice in the car, and NOT have rusting issues. Rust requires moisture, and if you're sensible heating 20 degree air, you have barely any moisture in the air.

Yes, turn it up to 110 ventilate the **** out of it and you will dry out every last crevice of the car. You will also have a huge energy bill, because to ventilate the **** out of it you will have to draw in cold dry air and heat it to 110. Very sensible.

You bring ice and snow into a garage which is below 32F and it will tend to stay frozen as ice and snow. You bring ice and snow into a 110F garage and it melt into water and then the water will evaporate and be in the air as water vapor unless you vent it to the outside. The air will be moister at 110F unless you vent it to the outside than it was below 32F with ice and snow laying around, because the ice and snow is now water vapor.

You will only barely have any moisture heating 20F air to above 32F if you do not have much ice and snow in the garage to start with. If you have enough ice and snow on your car when you bring it in, since air won't hold allot of water at 40F, the air won't be that moist, but your garage floor will end covered with water and where there was ice jammed into the crevices of your body work it will be wet and rust will be accelerated.

The net is, it is more sensible to leave your garage cold, and spend your money on washing the salt off your car more often than to try to heat you garage up to get rid of the moisture. Rust is accelerated by salt and water and it is more sensible to be more diligent about getting rid of the salt than it is to try to heat away the water.

 

[abbiepeach]

Hi nfamus10. Since you're still in the process of building your garage-condo, how often do you plan to use the place? I think the way you heat/cool your garage-condo depends on your usage and preferences, too.