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Large Patio Doors with Radiant Heat

Hello, thank you for all of the great info in the forum. I am building a new rambler house in Minneapolis. I am planning on doing all radiant heat, basement will be in the slab and the upper level will be in gypcrete. On the main level.

My big question is the HVAC contractor who our builder users highly recommended doing forced air on the main level in front of the large patio doors. I will have 3 16X8 4 panel patio doors on the main level. Can the hydronic provide enough heat to keep those patio doors frost and fog free?

My question to you all is do you need air movement over those large windows especially in a very cold climate like Minneapolis? My plan was to do a separate ERV/HRV system to move air in the winter time, and never use my forced air furnace which I will have to have to do AC in the summer.

My contractor wants to install a very expensive 95% eff furnace and hook the ERV into that ductwork. I would prefer to keep ERV/HRV on its own ducts as I do not want the furnace fan to have to provide ventilation.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 12,004
    Is the only reason to have a furnace to heat the patio doors, instead of using an ahu? Depends how much air the erv is handling.

    Ducting the erv with the furnace will pretreat the air which is a better idea in summer and winter.

    52 feet of doors is a big heat loss. I am leaning in the direction of your contractor.

    But I definitely would load up the radiant in the floor in front of those doors


  • TAG
    TAG Member Posts: 620
    What is the radiation -- slab/tile/wood. What's the heat loss of the room?

    What insulation type are you using? Any radon in the area? How humid in the shoulder seasons. How many people? Make up air?

    I have a large mostly glass room extending off my house (3 sides) and I have no problem heating it with radiant in the slab under the tile -- on its own zone.

    ERV/HRV are really for air change vs ventilation IMO -- I don't like using them for bathroom exhaust either. Radiant combined with a modern VS HVAC equipment is IMO the Cadillac of systems. The cost of running the fans is pennies ..

    Have been using spray foam for many years -- so my buildings are tight and need some air exchange. I have found a central intake 8" or 10" for both a dedicated dehumidifier and make up air for a large stove is an easy way to do it. Interestingly -- with the new VS fans on modern HVAC's .. the need for a dedicated dehumidifier has been greatly reduced -- depending on the people in the house the need for a HRV/ERV decreases. I still need the dehumidifier in the spring.

    I have made provision for an HRV/ERV in my last couple of projects just in case .... never needed them. I also have radon in my area -- so having some positive pressure is a plus.
  • Zman
    Zman Member Posts: 7,330
    I think this is going to boiler down to comfort. A door that big is going to have a heat loss of ~6,500 btu/hr plus the additional air leakage. If you go with tubing at 6" center in the 6' of floor in front of the door, that gets you ~8,600 btu/hr max. That combined with the rest of the floor should heat the space adequately. If the area in front of the door is a hallway, I would say go for it. If the area is a comfortable sitting area, the super warm floor on the feet and the cold glass next to your head is not going to be very nice from a thermal comfort point of view.

    If you decide to wash the area with warm air. I am thinking that using an ERV/HRV to dump low velocity air in front of the door makes sense. A hydronic fan coil in the duct would be an easy way to temper the air using boiler water. The key to that design is to size the coil to perform well at low water temps and to keep the air velocity down. Wind chill from high velocity heating air in an area like that is uncomfortable all the way around.

    Post more details of the space or plans if you can.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tonyholland00
    tonyholland00 Member Posts: 6
    Thanks for the input.. I really like the idea of the Clean Air furnace from lifebreath. It can give me the ERV and some air movement while using the boiler to the hydronic coil.

    I have attached the plans to this message. I am open to any an all ideas.
  • tonyholland00
    tonyholland00 Member Posts: 6

    Is the only reason to have a furnace to heat the patio doors, instead of using an ahu? Depends how much air the erv is handling.

    Ducting the erv with the furnace will pretreat the air which is a better idea in summer and winter.

    52 feet of doors is a big heat loss. I am leaning in the direction of your contractor.

    But I definitely would load up the radiant in the floor in front of those doors


    The reason for the forced air system is for AC in the summer more than anything.
  • Zman
    Zman Member Posts: 7,330

    Thanks for the input.. I really like the idea of the Clean Air furnace from lifebreath. It can give me the ERV and some air movement while using the boiler to the hydronic coil.

    I have attached the plans to this message. I am open to any an all ideas.

    That is what I had in mind. You put the air where you want it. Be sure whoever sizes the coil is using the correct supply water temp.

    Where are the main floor plans?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    tonyholland00
  • tonyholland00
    tonyholland00 Member Posts: 6
    Hello the main floor plans are in the the permit-2.pdf. The second page is the main floor. Thank you!
  • Zman
    Zman Member Posts: 7,330
    I think that you could go with in floor only for heating. Given your tight construction and significant kitchen hood, I would recommend installing an HRV or ERV with pass through capability equal to the hood CFM. It would make sense to use the same ducts as the AC. You could turn the distributing fan way down in the winter so you are just gently changing some air.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    tonyholland00
  • TAG
    TAG Member Posts: 620
    Trying to understand why you want to use two types of ducted -- a property designed ducted system can work perfectly with radiant. My new build will have various radiant floors. But, it also going to have full designed ductwork for AC -- the cost to make the AC a heat pump is pennies .. and I'm using a furnace vs an air handler again for flexibility and it only adds a few k.

    The new VS HVAC system are the way to go especially if you have low cooling loads part of the time and humidity

    Do you know the air changes you are going to use.

    My houses have big stoves ... so HRV/ERV don't work with 1200 cfms.

  • tonyholland00
    tonyholland00 Member Posts: 6
    TAG said:

    Trying to understand why you want to use two types of ducted -- a property designed ducted system can work perfectly with radiant. My new build will have various radiant floors. But, it also going to have full designed ductwork for AC -- the cost to make the AC a heat pump is pennies .. and I'm using a furnace vs an air handler again for flexibility and it only adds a few k.

    The new VS HVAC system are the way to go especially if you have low cooling loads part of the time and humidity

    Do you know the air changes you are going to use.

    My houses have big stoves ... so HRV/ERV don't work with 1200 cfms.

    I agree, I dont want to do two duct systems if I can avoid it.

    So do you guys have an opinion on the lifebreath ? I feel like that is the best solution so far for combination ventilation and supplemental heat via my boiler and AC. Any competent HVAC contractor should be able to install one of these right?

    Could you please clarify what you mean by VS HVAC? I am not sure what that terminology means.

    As for the hood, we rarely cook so i have asked that we don't get a monster cfm hood or anything like that.

    Thanks again for all the opinions.
  • tonyholland00
    tonyholland00 Member Posts: 6
    I see people have asked, but this is a house for my wife and I and a dog. We are planning a steam shower in the master bathroom.
  • gaabbee
    gaabbee Member Posts: 43
    "Could you please clarify what you mean by VS HVAC? I am not sure what that terminology means."

    I believe it means variable speed HVAC as in the fan can change speed based on load.
  • TAG
    TAG Member Posts: 620
    The lifebreath looks like an interesting product -- the question one always has to ask when encountering a "combined" product is what am I giving up (if anything) and at what cost?

    If you are doing a complete ducted system for the AC -- it must be important or you would not be spending the money. Other than the new Bosch units -- all the better systems use variable speed blowers (VS). How is the Lifebreath controlled ?

    My last two builds and my new one is using the Carrier 5 speed system -- zoned. Getting the heatpump version allows you use in the late spring and early fall when you don't want to turn on the radiant.

    Has you AC guy done a full load -- can the house be done w/o zoning?

    When I looked into getting the Carrier air-handler and adding the heating coil -- the cost of the furnace was not all that more .. and the boiler is not going to condense with the hot water needed for the coil. Totally integrated in both heating and cooling.

    I'm wondering how the Lifebreath is going to supplement the room w/ windows w/o zoning? If that's going to be the blower for the AC ?

    I like dedicated bath exhaust == fantech --- love the exterior wall mount w/ ducted intakes.

    Also -- Are you spray foaming. Are you doing a blower door test?