Author Topic: Considering Retrofit Radiant Floor Heating Project  (Read 1505 times)

chicagomeg

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Considering Retrofit Radiant Floor Heating Project
« on: May 02, 2023, 11:54:12 AM »
We recently purchased a tri-level style home in Chicago & are considering adding radiant flooring in the lower levels to improve comfort in these rooms as well as adjacent ones. I work from home full time so the house is occupied pretty much 24/7 and the lower half can be quite chilly.

Here's the existing equipment we're working with:
  • 2005 natural gas forced air furnace of unknown efficiency
  • 2022 natural gas storage tank water heater, 80% efficiency
  • I don't know jack about circuit breakers, but I did identify that ours has 5 empty bays so I think we can handle a moderate additional electrical load

There are 3 rooms we are considering eventually adding radiant flooring to. The den is the first priority that I'd like to work on this summer, with the office a 1-2 years from now project and the guest room more questionable, depending on results & other priorities.
  • The den is ground level with hardwood flooring on a plywood subfloor. The joists and subfloor are exposed beneath in a semi-finished crawlspace/storage area and this room is adjacent to the existing utility room. This room is about 250sq ft and is typically 5-10 degrees cooler than the main floor.
  • Husband's office is basement level, with a peel and stick tile floor on some type of subfloor, over a concrete slab (I assume). It adjoins the storage area that is under the den. This room is about 200 sq ft and can get as cold as 50 degrees in the winter (15-20 degrees cooler than the main floor). My office is above this space and is also pretty chilly, especially in the mornings.
  • The guest room is ground level with carpet on (I suspect) a subfloor over a concrete slab. I haven't monitored temperature in here as closely but it's not unbearably cold and the living room over it tends to be the warmest room in the house. I'm inclined to leave it be for now but if we added a zoned hydronic pump I'd probably buy a 3 zone one to allow us to add heating here someday.

With those requirements in mind, I'd be interested in folks opinions on the following:
  • Is radiant flooring a reasonable solution in this situation or should we consider upgrading the near end of life HVAC to a multi-zone system for the same effect?
  • Should we do a hydronic or electric system in this situation? I think the electric system is overall easier and would be great in the office, but I'm a little skeptical it will get warm enough to penetrate through the subfloor & hardwood floor in the den.
  • If we do a hydronic system, can we use our existing water heater? I can't make the math math to replace this one with a more efficient heat pump or tankless one at this time.

bill1827

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Re: Considering Retrofit Radiant Floor Heating Project
« Reply #1 on: May 03, 2023, 03:57:29 AM »
Unless you are prepared for an enormous amount of disruption I wouldn't do it. You need to have very good insulation under the heating elements (something like 8" of PUR) otherwise most of the heat will disappear into the ground. That mean digging up the concrete floors to a depth of about 12" to accommodate the insulation and a new slab. You could put insulation on top of the existing floor if you can live with the change in level and reduced room height.

Don't use electricity; it's likely to be the most costly and most polluting heating method. You could use an ASHP if you were to go with a water based system but that would need careful design. Your existing water heater won't be usable.

By the sound of it a split system is likely to be the best option; easiest to install, cheapest and probably most efficient. It also comes with cooling ability if you need that.

lthenderson

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Re: Considering Retrofit Radiant Floor Heating Project
« Reply #2 on: May 03, 2023, 04:42:40 AM »
Retrofitting radiant heat flooring under your den floor is a lot of work. My solution would be just to use throw rugs in that room and/or slippers when it is cold.

Electric is definitely the easiest way to go for the office. Unlike the commenter above, I have installed electric radiant flooring in two bathrooms and they both work well and there is a negligible amount of heat produced in the room below. Both bathrooms had cement board installed over the subfloor, then the radiant mesh installed on that followed by tile. It is so nice to walk into the bathroom on a cold winter morning with bare feet and have a nice warm surface to greet you. Bathrooms however, are much smaller rooms than a office probably is, so you would have to take into account the power draw for doing an entire room. With our bathrooms, we only installed it in the areas where we would be walking, about a quarter of the entire bathroom size.

CatamaranSailor

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Re: Considering Retrofit Radiant Floor Heating Project
« Reply #3 on: May 03, 2023, 06:24:07 AM »
Radiant heating does not need to be limited to the floor. You can add radiant to walls and ceilings. There are also pregrooved panels available that have channels cut for the tubing and reflective barrier built in to reflect the heat. Hella expensive though!. That being said (and having done radiant heating and loved it) this is what I would do in your situation.

  • Get an energy audit done. A lot of utility companies will do it for free.
  • Good old fashioned air sealing. Drafts destroy comfort no matter how good the heating system
  • Look at areas that can be insulated easily and do it

All of that can be done easily and cheaply. It also can make a huge difference on indoor comfort.

To retrofit with radiant you'll need a heat source. A standard furnace will not work, which means a boiler or a hybrid hot water heater that has space heating capability. Those are pricey. You'll nee to run tubing through joists bays or into the panels I described above. Again, this doesn't have to be into the floor. You need pumps, a manifold and a controller.The system also has to be sized correctly based off heat loss calculations.

All of this is doable. But it will be a big project even for just a couple of rooms.

You'll also end up with kind of a Frankenstein heating system. It may work fine, but if you ever sell...explaining all the different ways you heat the house to a buyer could be challenging.

As a fan of radiant heating I'd encourage you to research it carefully, but in the end, in my limited opinion, retrofitting the whole house with a split is going to be the way to go.

But if it turns out radiant makes sense...it's doable and there are companies like Radiantec that will help with all phases.

Good luck!


NaN

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Re: Considering Retrofit Radiant Floor Heating Project
« Reply #4 on: June 02, 2023, 06:35:18 PM »
I do not think it is a reasonable solution. Stick with your forced air.
Don't go electric resistive heating. It is not that efficient in converting electricity to heat. A heat pump is much more efficient.
No, you need a boiler, which could serve your domestic hot water if sized appropriately.

GilesMM

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Re: Considering Retrofit Radiant Floor Heating Project
« Reply #5 on: June 03, 2023, 05:53:44 AM »
You didn't mention AC, but if the unit is as old as the furnace I would replace both with a heat pump. Then have a go at your duct work to fix the issues you mention.  You may need to have professional install baffles or other duct bits to balance the air supply.  Or, you may be able to do it yourself by adjusting the flow from individual registers.  Reduce flow to upper level rooms in winter so more goes downstairs.  Keep the lower level doors shut so all the heat doesn't go upstairs.

 

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