ETS or Staple Up Hydronic Infloor Heating for a Crawlspace

[ChronicHydronic]

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]

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]

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]

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]

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.

 

[ChronicHydronic]

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]

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]

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]

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]

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]

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.

 

[DBoon]

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]

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]

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.

 

[ChronicHydronic]

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.

 

[ChronicHydronic]

Infloor Hydronic Update: Have replaced 1/2 the first floor floors and getting ready to lay 1/2" pex.

I am trying to heat my first floor only (about 500sqft.)

Section A: 250sqft of old rotten floor boards have been torn out and replaced with plywood. The pex will go down between 3/4 ply sleepers in aluminum plates and be covered with 3/4" thick finish floor pine boards . So 3/4" plate to foot separation

Section B: 250sqft of decent spruce and pine floor boards totaling less than 1 3/4" thick will be left as is and the staple up pex method with the same plates will be used under the subfloor. So 1 3/4" plate to foot separation

Insulation is planned under the whole floor.

My plumber has suggested A and B should be 2 different zones and a mixing valve will be required since Section B has about 3/4" more wood for the heat to go through than section A.

I am wondering if this is really necessary and if the difference in final floor temperature (from 3/4" pine difference) can be taken up by ball valve adjustment at the return manifold without having a mixing valve?

It seems like a shame to mix down the temperature in Section A as this is the family room and the room we are especially wanting to heat.

In terms of complexity, if we didn't need a mixing valve, I would probably do the following.
. Put section A and B on the same zone so zone valves would not be required
. I could go with one circ,. pump as I imagine, a second would be needed to pump away from a mixing valve, if required
. One thermostat could do the trick and I wonder if I would need a Tekmar 302 or 303 type controller if no zone valves were in the design.

Should be noted this is the 130 year old cottage so we plan to be here 1/2 of our time.

I would greatly value the qualitative judgement of those on the forum on this mix...or no mix issue.

Other issues I am struggling with is whether to put antifreeze in the system. We are getting hit by hurricanes every year now.
And the big one; propane combi or electric on demand boiler; Decision drivers; cost to buy/install/operate/maintain, fuel price stability in the future, best system for cottage use, etc.etc

The last two have likely been covered by this forum so I'll do some digging on those.

 

[DBoon]

Hi ChronicHydro, I've been missing from here for a while, so I hope my post doesn't come too late to be helpful.

I would go with the two zones. You don't want your total PEX pipe runs to be longer than 250-300 feet in length each. You might even need more than two zones. More is not worse, and it won't take much more time to run more zones. Better to keep the loops at 250 foot length or shorter. This will be hard to do in a room that is 250 square feet, but easy to do for half that square footage.

A mixing valve is the way to go. You'll get the best control to balance the two areas. You'll have a manifold also (I am guessing) that will provide some basic balancing using some flow control valve. That's ok for tuning it a bit, but the mixing valve is a better solution.

One circulation pump should be all you need. It works for me and I have nine loops. Go with a Grundfos Alpha2. It will pump away from your tank/boiler) (located after the expansion tank) and into the zones. If it is a pump like the Grundfos, it will just ramp up the speed as the zones open up.

Water+Antifreeze mix will reduce your heat transfer. I'd stay away from it. But it might be necessary if you are at high risk of losing power and you aren't there 100% of the time.

 

[ChronicHydronic]

Hi ChronicHydro, I've been missing from here for a while, so I hope my post doesn't come too late to be helpful.

I would go with the two zones. You don't want your total PEX pipe runs to be longer than 250-300 feet in length each. You might even need more than two zones. More is not worse, and it won't take much more time to run more zones. Better to keep the loops at 250 foot length or shorter. This will be hard to do in a room that is 250 square feet, but easy to do for half that square footage.

A mixing valve is the way to go. You'll get the best control to balance the two areas. You'll have a manifold also (I am guessing) that will provide some basic balancing using some flow control valve. That's ok for tuning it a bit, but the mixing valve is a better solution.

One circulation pump should be all you need. It works for me and I have nine loops. Go with a Grundfos Alpha2. It will pump away from your tank/boiler) (located after the expansion tank) and into the zones. If it is a pump like the Grundfos, it will just ramp up the speed as the zones open up.

Water+Antifreeze mix will reduce your heat transfer. I'd stay away from it. But it might be necessary if you are at high risk of losing power and you aren't there 100% of the time.

Hi Thanks Dboon, Your comments are timely as the soldering stage is close. I enclose a pic of the possible layout. Yes I have the two zones and mixing valve on Zone 1. Manifold flow control on the return. My reading suggests it is impt to pump away from the mixing valve ...hence the layout displayed. I, m not sure how impt. this is as out house system has been pumping into a mixing valve for 20years or so with no problems. If it is not that impt. I would put the pump before the T off to Zone 2 .....which seems like a better location.

I'm new to all this so other ...better design ideas are welcomed.

I have a number of older Grundfos pumps and decided to use the 3 speed so I can adjust it a bit. While I like the idea of the variable speed pump, I'll be pulling 50amps of power from the electric boiler so my main goal will be to insulate etc. to try to keep that thing off as much as possible. (I eventually gave up reviewing all the bad boiler/fuel/installation options and went with the cheapest until the world settles down).

I also don't like the idea of antifreeze and will go without to start.
Thanks again!