ETS or Staple Up Hydronic Infloor Heating for a Crawlspace

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ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
Hi Guys, I'm a new member that enjoys reading all your great posts.
Recently bought a 130 year old ....leaky house with a 4' high crawlspace. NS Canada.
House has electric heat and I added a wood stove insert to the main floor.
This combination heats the second floor, but the floors on the first floor are unbearable in the winter.
The underlying crawlspace has a vapour barrier on the floor and spray foam on the walls so not bad.
I need to seal off the access door better and control water leakage and humidity down there.

My first thought was to use the staple up and aluminum fin method to heat the 2- 3/4" layers of pine wood floor. I got bogged down in the few cheap options out there to provide hot water for this system. I also had some advice from a plumber who had done this a number of times.......he said use any other heat source rather than hydronic radiant. I think this relates mostly to the wood being more of an insulator than a storage device like concrete. I love this concept, however, so would be interested to hear from people who have installed this and love it too. I would actually spray foam under the joists after the install so this would help alot as well.

An alternative option I am looking at is ETS system(s) using off peak rates. These could go on the first floor but I am wondering if it would be better to put them in the crawlspace? In this case, I think I would spray foam the floor and then the crawlspace would be a completely conditioned space. Is this a good idea? Would this heat make it's way through the floor and up into the first floor area? The main house footprint is about 600 sq ft (1200 overall) so not overly large , but I only have a 100amp panel. Currently the electric baseboards take up 80 amps.

I'm interested in finding out the best option for this old place ....that may not include either of these. I should mention this is a cottage (don't want to break the bank) but we use it year round.

Many Thanks
 

stoveliker

Minister of Fire
Nov 17, 2019
4,353
Long Island NY
I would spray the underside of the floor, i.e. the "ceiling" of the crawlspace. Any heat you put in the first floor room is going to have fair losses to the crawlspace, regardless of how much the crawlspace is insulated on the walls - the cold ground will suck up a lot of BTUs.

So, insulate the floor, then add heat on the first floor where necessary. Adding heat before stopping that large heat leak to the crawlspace is going to be relatively ineffective (i.e. relatively expensive).
 

ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
I would spray the underside of the floor, i.e. the "ceiling" of the crawlspace. Any heat you put in the first floor room is going to have fair losses to the crawlspace, regardless of how much the crawlspace is insulated on the walls - the cold ground will suck up a lot of BTUs.

So, insulate the floor, then add heat on the first floor where necessary. Adding heat before stopping that large heat leak to the crawlspace is going to be relatively ineffective (i.e. relatively expensive).
There are trade offs to every plan it seems. If I go spray foam first it negates ever putting in hydronic heat or ETS units in the crawlspace. I also don't love the idea of burying all my wiring and piping. But insulating the floor may allow me the comfort I need even with the existing electric baseboards.........so this may be the best solution.

However...........after spending 6k on a wood stove install, I would like my next move to be the last one. Anyone have any experience with the infloor staple up method through 1.5" of pine or ETS units in a crawl space?
 

EbS-P

Minister of Fire
Jan 19, 2019
2,420
SE North Carolina
I see radiant floor heat as a luxury item. It’s single function(just heat). Adding a whole new hydronic system seems costly.

Restive electric under new LVP would be my route if I really wanted the comfort. We have it under tile in our bathroom. The floor never feels warm unless I crank the thermostat way up, but it’s never cold under foot. If floor is well insulated it shouldn’t be too cold.

Cheapest option probably is batt insulation (Theymake a mineral wool panel insulation that can be fastened to the bottom of joists) and a mini split heatpump. Or just lots of insulation. I don’t see how off peak rates could beat the operating cost of a heatpump.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,198
South Puget Sound, WA
Cheapest option probably is batt insulation (Theymake a mineral wool panel insulation that can be fastened to the bottom of joists) and a mini split heatpump. Or just lots of insulation. I don’t see how off peak rates could beat the operating cost of a heatpump.
That is what I am thinking, It may need to have a cover screen or skin if vermin are an issue. If the crawlspace is totally dry it might be worth exploring turning it into a conditioned space. This would require a vapor barrier, sealing the vent, insulating the walls and rim joist. This is how our house is set up once we had a proper foundation. It really made a difference in warm floors and I have full access for wiring, plumbing, etc.

A mini-split + wood stove is a sweet combo and probably the most cost-effective.
 
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ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
Thanks Guys for the comments. The reason I was leaning towards spray foam is that every joist bay is a different width, Anywhere from 8" to 20". This would be a lot of upsidedown work and waste. Gotta love a 130 year old home! Also I need to get the moisture under control as I'm concerned about mold and of course squirrels and worse getting into batts.

If I spray foamed the floor and put in a good tight access door, I'd get a great vapour barrier as there is already one down. This would become a conditioned space as begreen mentioned. Did you put the minisplit in the crawlspace or on the first floor to get those nice warm floors?
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,198
South Puget Sound, WA
Our house is coming up on 100 yrs old. Farmer built. The house sat on a hodgepodge foundation that had been shored up on the downslope and with the sill on dirt on the upslope side. Naturally, there were gaps under the rim joist (solid 8x8) and in some joist bays. In 2006 the house was lifted up 6 ft and a new 3' high foundation was poured, then the house was set down on it with a foam gasket in between the rim joist and the foundation. I spent a week with caulk and spray can foam sealing up all gaps around the rim joists and joist bays. Then the inside of the foundation was insulated with foam sheets. The result has been a crawlspace that never drops below 55-60º. That has led to much warmer floors. The crawlspace has no forced ventilation. The foundation has vents that were required by the county. They are closed and I open two in the summer. Note that our summers are dry and not humid so condensation is not an issue. A good new gutter system makes sure water is drained away from the house and our soil is sandy and dry.
 

ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
Thanks begreen , Sounds like we both have lots of work ahead of us.

Did your foundation include a poured concrete floor or just a vapour barrier over ground? My floor is the later. The walls are very irregular bedrock and or placed stone, but they and the rim joists are spray foamed very well.

My main problem is the outside access door is very leaky. This will be fixed this summer.

I monitored the temp down there over this winter 3-6 Degrees C so 38-42 F?

Did you insulate the joist bays ? or do you heat the crawlspace? or just allow the heat from the first floor to heat up the crawlspace?
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,198
South Puget Sound, WA
Just the footings and walls. The house now sits 3' higher than previously. The vapor barrier is over the dirt floor. Yes, I batt insulated all of the joist bays.
 

stoveliker

Minister of Fire
Nov 17, 2019
4,353
Long Island NY
One important thing to keep in mind is that joist bay insulation does need an airtight barrier first. As in spray foam and then batt. Or foam panels where the seams are foamed shut, before adding batt insulation. Otherwise the joist may not.
 

mcdougy

Minister of Fire
Apr 15, 2014
794
ontario
If your temperatures are that low in the crawlspace I would assume that the access door you keep referring to is the main culprit. Seal it up and buy a pair of slippers ( just in case) for next winter. You might find that the door is the source of all the discomfort. Also once you find a nice a pair of slippers you will love them. :) You might have your issue solved for fractions of the cost of another heating system.
 
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DBoon

Minister of Fire
Jan 14, 2009
1,280
Central NY
Anyone have any experience with the infloor staple up method through 1.5" of pine or ETS units in a crawl space?
Yes, I do. It will work. I have radiant heat working through 7/8" pine plank and 3/4" oak or fir (different by floor). I used 1/2" pex installed in thick aluminum plates. You have to fit the plates tight to the floor, so plan on grinding all the nails that protrude through the bottom of the floor. I have insulated to R-19 below the plates, between the joists. My max water temperature is 120 degrees. Whether this will provide all the heat you need or not depends on your building envelope. Carpets (area or wall-to-wall) will reduce the heat transmission by a factor of 3 or so, which will make it impractical if you have carpets.
 

ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
Yes, I do. It will work. I have radiant heat working through 7/8" pine plank and 3/4" oak or fir (different by floor). I used 1/2" pex installed in thick aluminum plates. You have to fit the plates tight to the floor, so plan on grinding all the nails that protrude through the bottom of the floor. I have insulated to R-19 below the plates, between the joists. My max water temperature is 120 degrees. Whether this will provide all the heat you need or not depends on your building envelope. Carpets (area or wall-to-wall) will reduce the heat transmission by a factor of 3 or so, which will make it impractical if you have carpets.
Hi DBoon I missed your reply. Thanks for the hands on experience and this looks more promising as I have sourced most of the (used) parts for a hydronic setup. Are you using a water heater as your boiler as you mention a 120 degree limit? If so, do you have separate tanks for DHW and hydronic?

Can you comment on the efficiency or costs of running your system through wood floors?
I have toyed with the idea of building plywood trays 2" below the top of the joists and using the gypcrete method up to the top of the joists and then cover with wood. This would be loads of extra work /engineers/cost but would give us the thermal mass that would hold heat longer than wood. I'm likely inclined to go your method.

If so , also wondering about an on demand propane Combi unit. That would take out our water tank and also allow for higher temps should we need it for hydronics.

Thanks for the comments about carpets. We do have area rugs mainly to try to keep our feet isolated from the cold floors. If the hydronic system was successful, I'd gladly get rid of the rugs. And for a previous post, I do have nice slippers but was wondering about attaching 2" pieces of rigid foam to the bottoms. Could save us all alot of money!
 

DBoon

Minister of Fire
Jan 14, 2009
1,280
Central NY
Hi ChronicHydro,

You first need to do a heat loss of your home, room-by-room. I did mine using Excel and provided all the math for heat loss through walls, windows, floors, etc. It will allow you to plan your system. Radiant under wood floors (without carpets) works fine for heat supply of 15 BTU/square foot or lower at your outdoor design temperature. Mine is about 10 BTU/square foot (I have a fairly well insulated and very tight house). Each loop should be 300 feet or less. I would recommend using 1/2" pex and the thick aluminum plates. And you must insulate under the plates. Don't pour another floor on top - you would just be wasting your time and money.

My heating supply is a geothermal heat pump. DO NOT use a water heater for your heat supply (and don't do anything else that Radiantec recommends). A water heater is not rated to heat a house and the flow resistance of a water heater is too high for effective operation. I have a storage tank that the geothermal system heats up and that feeds my radiant loops. My water design temperature (to heat the house) is 120 degrees at 0 degrees outdoor temperature (to meet my heat loss heating needs). You don't want to go much above this for wood floors - I have mine set to not exceed 127 degrees F. I have a separate DHW tank that has it's incoming cold water supply preheated by a heat exchanger in the storage tank.

If you use a propane combi tank, you'll need to install a tempering valve and then have the tempering valve control the temperature through an outdoor reset (ODR) to the radiant loops. And use a small pump, like an Alpha2 by Grundfos - it's all you'll need (likely). You want the water to flow constantly at just the right temperature to keep the floors warm but not hot all the time. The small pump is really efficient at doing this. The more accurate you can calculate the heat loss for each room, the better you can design the system to supply just the right amount of heat to each room so they are comfortable.

OK, the downsides. This is the most comfortable heat you'll ever experience. It is also a real pain-in-the-ass to install. The availability of contractors who will design it and install it correctly is low (my opinion, at least in my area). I learned everything about it and designed it myself and installed it myself. It works great, but it was time-consuming.

www.heatinghelp.com is a great resource for this. I posted about my system there https://forum.heatinghelp.com/discu...me-feedback-on-my-radiant-design-plans#latest
They are very willing to help, but you have to be willing to do the research and put in your own work to get your system right.
 
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ChronicHydronic

New Member
May 11, 2022
6
Nova Scotia, Canada
Many thx DBoon, Went over to heating help and read all your posts. Great info. I will have questions, but need a day or to organize and re-read. Love to see a pic of your setup as I also plan to do this myself.