Old house and radiant heat.

[coolidge]

Not shure if this belongs here or not but here goes. I've got an old house( 1890's) with the paper between the subfloor and hardwood. I have herd if you install radiant in this situation the paper smells really bad. Anyone herd of this or experianced it.

Thanks

 

[dgold]

If the radiant heat manufacturer has a tech help line, I'd give them a call. Who knows, maybe certain temperatures trigger the smell or something like that. They may be able to make a recommendation. I'd call several different radiant manufacturers to see if any can specifically address your issue.

 

[Gooserider]

This seems more like the kind of question the Boiler Room folks would be able to handle, so I'm going to bump it over there...

Gooserider

 

[Chris S]

tar paper will give off odor , rosin paper is OK. If you have tar paper which is that old , you may be OK. This is just a guess on my part , but the paper I've pulled up in older buildings doesn't have much to it. It's the oil you're worried about, and in the really old stuff- there isn't much there.

 

[DaveBP]

How about an experiment?
If you have access beneath the floor anywhere put an electric heating pad up against the subfloor and press it up with some insulation scrap and a couple screws or something like that to get decent contact between the heating pad and the bottom of the subfloor. Crank up the heating pad until the floor above is noticeably warm. Put a clean cardboard box over that spot and let it sit for awhile. Then gently lift up the box and smell inside it.
If a cat ever peed on that spot in the last 90 years you may need to move your experiment to another location.
The rule of thumb for radiant floors is that you never heat them to higher than 85F (at the top surface) or they will feel uncomfortable underfoot. That's really no warmer than a spot of floor with the bright sun through a window on it. Tar paper is a no no.

 

[coolidge]

Thank You all, I took a core sample and found it to be red rosin paper. I guess i,m good to go.

Thanks

 

[pybyr]

One last thing - be sure that the floor is not so thick that it defeats the heat's ability to get through to the living space (I've seen lots of old buildings where new floors were added on top of old floors resulting in 3 or more inches of wood between cellar and the upper side of the floor).

With radiant heat under a wood floor, there's an upper limit (and it's cooler than tile, etc.) of how hot you can run the water through the tubing without getting into issues with the wood - and if you combine that with a really thick wood floor that resists heat transfer, it may be hard to move all the BTUs you need to heat the house under cold conditions.

Wood isn't great insulation when compared to modern insulating materials, but I recall that average wood has an "R" insulating value per one inch of thickness.... thus a 3 inch thick floor is like having R-3 insulation between your radiant tubing and the living space.

Disclaimer- I am not a professional at this, but I have a n 1840+/- house and have looked into these issues a bunch due to my hope to maybe eventually add radiant floor heat.

 

[Como]

I looked at this and chatted with a few manufacturers, generally better to go with radiators and/or baseboard.

 

[Gooserider]

I looked at this and chatted with a few manufacturers, generally better to go with radiators and/or baseboard.

The cynical part of me wonders if said manufacturers produced radiators and baseboards... :coolhmm:

My feeling is that it seems somewhat difficult to get good heating at low design temps unless using those large radiant panels (which I think have their own issues in many spaces) or infloor radiant... But it appears to me that efficiency and burn times suffer at high design temps because you don't have as wide a temperature swing to utilize storage effectively - which makes me think that if doing a wood boiler it is best to design around a 120* distribution temperature if possible (this also makes solar water heating a reasonable option for some) To me this calls for radiant panels or infloor. Since I don't like the large sizes of the radiant panels...

I am also looking at retrofitting radiant, but I know that I don't have overly thick floors to deal with, (3/4" subfloor decking w/ one layer of particle board or plywood over it, now carpetted, but the rugs need replacing, likely to go for laminate wood floors, but not certain... I'm undecided about trying to go with staple-up from the basement, or ripping out the particle board down to the subfloor and putting in some sort of warmboard equivalent, either manufactured or home-brew... Most of the house I feel quite sure the underfloor would be adequate, but I'm sort of worried about the living room, as it has a very high cathedral ceiling (about 26' at the peak) fairly high heat loss numbers, and a smallish floor space. It looks like I'd be needing to get at least 80 BTU/sq ft/hr out of a floor, which is pushing things a bit w/ staple up. OTOH, I don't see how to do above the subfloor without raising the height of the LR floor above the rest of the rooms on the floor by 1/2" or so, which I also find objectionable...

However if I did have a situation, like pybyr mentioned, of an extra thick floor, I would be inclined to lift the top layer, and rout out the grooves for my tubing in the layer under it, then recover - depending on what was underneath, I might even go down a couple of layers if the older floors were particularly nice and could be salvaged...

Gooserider

 

[coolidge]

I have been studying the floor thickness and found it to be just the subfloor and hardwood on top. I'm not oo shure which way i,m going to go yet as my floor joist are "logs" and spaced anywhere from 2 feet too 36". Still sturdy for the age. I have talked with a few dealers and installers that are recommending an extra loop between bays, a good idea with space of the stringers. The design temp is going to be around 120 degrees. A concern i have is am i going to be overkilling this setup. I am in the process of ripping out all the exterior walls on first floor and the little insulation (cellulose) left and replacing with R-28 sprayfoam along with new windows. Any thoughts, comments? I have been trying to get my buddy who does energy audits over but it is that time of year and he is out straight with no end in sight. One last question. I have found what i think is a good buy on 1/2 o2 pex on e-bay. 1000ft for 275.00. Has anyone used or had problems with ordering from e-bay?

Thanks

 

[DaveBP]

Air infiltration on those old houses can be nearly half the heat loss when the winter winds blow. Closed-cell foam is probably the best for insulation/installed inch of thickness and for closing up all those thousands of air gaps. If you are in the house for the long term I think the money (and it will cost a lot) is well spent. The constant payback is both in comfort and less money spent on heating for the rest of your life and for the next owner, too.

If you are putting the tubing under the subfloor I think you should try for a spacing of 8" between parallel tubes and use at least the sheet metal aluminum heat spreaders fixed tightly to the subfloor above. The faster you can spread the heat out and through the flooring to the living space above - the cooler you will be able to run the water temperature. Cooler water is better. It's not easy to cram a lot of heat through all that wood and it will be very difficult to add more tubing later. Once you've had the experience of feeding all that tubing through all those holes in the joist bays you'll know what I mean.
Here's a very good article about this topic from a well known pro:

(broken link removed to http://www.radiantengineering.com/PlatelessInRadiantville.pdf)

I've had only a few Ebay experiences and they've all been good. However, there are a lot of PEX tubing brands out there now coming from China and India. I just have trouble trusting their quality control systems for something that needs to last a long, long time. I also have lost faith in American labeling regulations and enforcement to ensure that sourcing information is available to the end user. I would have to give the benefit of the doubt to the European brands. But it's not my money you're considering and it may be perfectly good stuff you're looking at.

 

[Sting]

I have been studying the floor thickness and found it to be just the subfloor and hardwood on top.

With that in mind -- you may wish to consider a combination system with different circulation temperatures and control to the in floor and the (radiators or baseboard)

See you will NEVER get enough pex stitched under that floor system to radiate enough energy to obtain a comfortable room

BUT

You will be easily able to get enough to make a nice comfortable warm floor and that will really be nice!

 

[Gooserider]

I have been studying the floor thickness and found it to be just the subfloor and hardwood on top.

With that in mind -- you may wish to consider a combination system with different circulation temperatures and control to the in floor and the (radiators or baseboard)

See you will NEVER get enough pex stitched under that floor system to radiate enough energy to obtain a comfortable room

BUT

You will be easily able to get enough to make a nice comfortable warm floor and that will really be nice!

Not sure I buy that - it all depends on the total room loss (which ought not to be that bad w/ spray foam insulation) vs. room size - staple up radiant floor w/ aluminum plates is supposed to be good for about 40 BTU / Hr / sq. foot, and if that works from a numbers standpoint, I don't know why it wouldn't make for a comfortable room...

It would seem that if the OP's floor stringers are on 2-3' centers, it should be quite possible to average 8" tube spacing, though the number of passes per bay will vary, and that might make planning the layout a bit tricky. I don't know if there are any "rules" on minimum allowable spaces that say you can't go closer than 8" - if there aren't, I'd be tempted to go for four passes per bay, spreading as evenly as I could. Would use more tube (and possibly require more headers for additional loops) but I don't see any other problems with that - might even allow use of an even lower maximum design water temp, which would be a good thing...

Gooserider

 

[heaterman]

I don't know if this is an option for you but there are some really good above floor products available if you aren't concerned with keeping the present floor covering. If you have some nice old oak or maple flooring it would be a shame to cover it up. At any rate, both Viega and Uponor (Wirsbo) make an excellent above the floor product. I like it for a couple reasons. The response time is measured in fractions of an hour instead of half a day like all the subfloor product I have encountered. The other factor is that it allows you to run pretty low water temps. The system in my house (Viega) runs between 85* up to 115-120* based on how cold it is outside. That's a far cry from the 140-160+ range you'll need to transfer 25 btu/sq ft from a subfloor system, especially if you have a couple inches of wood on it and maybe some carpeted areas. I do have a couple systems running subfloor applications and they will put out some heat under tile or wood flooring. I wouldn't advise it for true heating purposes under any type of carpet. It'll warm it up but the max output is realistically in the 10-15 btu/sq ft range. Most old houses need substantially more than that. For retrofit jobs I usually try to recommend panel radiators for nice variable heating output. An on/off baseboard system would be low on my list.

 

[Sting]

Goose -- You are correct again -- but those ratings are for staple up with plates under the new code OSB sub flooring of the "modern" construction practice of today.

Dealing with old houses -- full cut old growth thick sub floor boards sheeted on the bias then covered with ???? and finally over nailed with full thickness hard wood floor!

Well 00 the transfer efficiency just isn't there. I did a job where the finish floor of the old place was nailed on sleepers with coal slag sand poured over two layers of 30 lb tar paper, over the sub floor of one inch by 8 to 16 inch wide boards. The floor almost got warm circulating 140 degree water for days. Boy, did I have some "splaining to do" Quote Ricky to Lucy

A lucid heat loss calculation will hold the answer - An effective insulation program will help, but often that will destroy the ambiance of the old home ( so why bother - just tear it down and start over) I believe in old houses, the Old dead Plumbers had the correct approach - overkill on the radiation! In this case, the customer will really enjoy the warm floor and radiators, heavy baseboard or panels as Heaterman suggests (not on the reduced temperature leg of the infloor) will provide the comfort and heat makeup necessary during those couple of weeks of winter when the heat load is the highest. Just build the system so you don't circulate water bearing liquid with a higher energy content tha necessary and you won't have a bang-bang of on/off system as above! Out door circulation temperature resets are your friend!

Kind Regards
Sting

 

[Gooserider]

Goose -- You are correct again -- but those ratings are for staple up with plates under the new code OSB sub flooring of the "modern" construction practice of today.

Dealing with old houses -- full cut old growth thick sub floor boards sheeted on the bias then covered with ???? and finally over nailed with full thickness hard wood floor!

Well 00 the transfer efficiency just isn't there. I did a job where the finish floor of the old place was nailed on sleepers with coal slag sand poured over two layers of 30 lb tar paper, over the sub floor of one inch by 8 to 16 inch wide boards. The floor almost got warm circulating 140 degree water for days. Boy, did I have some "splaining to do" Quote Ricky to Lucy

A lucid heat loss calculation will hold the answer - An effective insulation program will help, but often that will destroy the ambiance of the old home ( so why bother - just tear it down and start over) I believe in old houses, the Old dead Plumbers had the correct approach - overkill on the radiation! In this case, the customer will really enjoy the warm floor and radiators, heavy baseboard or panels as Heaterman suggests (not on the reduced temperature leg of the infloor) will provide the comfort and heat makeup necessary during those couple of weeks of winter when the heat load is the highest. Just build the system so you don't circulate water bearing liquid with a higher energy content tha necessary and you won't have a bang-bang of on/off system as above! Out door circulation temperature resets are your friend!

Kind Regards
Sting

You sound like you have had far more experience with this stuff than I have, so no real arguement. I was going by the OP's earlier comment five or six posts back, that he had been looking at the floor and thought it was one layer of subfloor plus hardwood... Admitedly he didn't say how thick the subfloor or the hardwood was. If it's around 1" each like the modern stuff seems to be then it might be OK w/ just radiant, or possibly not...

It also seems like there is a lot of difference of opinion about what kind of heat output one can get from a staple up radiant setup. I have seen the 40 btu / hr / sq ft, (w/ 120*F water) number thrown around in various places, but I see Heaterman saying 25, and needing a higher water temperature... This is rather confusing, :-S what does one need to get a definitive answer - assuming 1/2" tube, light weight AL plates, and insulation under the tubes...

Since I'm trying to decide on what to do for my own setup, this is more than just idle curiosity...

I also should say that I have a strong bias against panels in most living spaces because I don't like giving up the wall real estate for them, not to mention that IMHO they are *UGLY* so I'd really want to try hard to avoid them.

Gooserider

 

[Fred61]

I looked at this and chatted with a few manufacturers, generally better to go with radiators and/or baseboard.

The cynical part of me wonders if said manufacturers produced radiators and baseboards... :coolhmm:

My feeling is that it seems somewhat difficult to get good heating at low design temps unless using those large radiant panels (which I think have their own issues in many spaces) or infloor radiant... But it appears to me that efficiency and burn times suffer at high design temps because you don't have as wide a temperature swing to utilize storage effectively - which makes me think that if doing a wood boiler it is best to design around a 120* distribution temperature if possible (this also makes solar water heating a reasonable option for some) To me this calls for radiant panels or infloor. Since I don't like the large sizes of the radiant panels...

I am also looking at retrofitting radiant, but I know that I don't have overly thick floors to deal with, (3/4" subfloor decking w/ one layer of particle board or plywood over it, now carpetted, but the rugs need replacing, likely to go for laminate wood floors, but not certain... I'm undecided about trying to go with staple-up from the basement, or ripping out the particle board down to the subfloor and putting in some sort of warmboard equivalent, either manufactured or home-brew... Most of the house I feel quite sure the underfloor would be adequate, but I'm sort of worried about the living room, as it has a very high cathedral ceiling (about 26' at the peak) fairly high heat loss numbers, and a smallish floor space. It looks like I'd be needing to get at least 80 BTU/sq ft/hr out of a floor, which is pushing things a bit w/ staple up. OTOH, I don't see how to do above the subfloor without raising the height of the LR floor above the rest of the rooms on the floor by 1/2" or so, which I also find objectionable...

However if I did have a situation, like pybyr mentioned, of an extra thick floor, I would be inclined to lift the top layer, and rout out the grooves for my tubing in the layer under it, then recover - depending on what was underneath, I might even go down a couple of layers if the older floors were particularly nice and could be salvaged...

Gooserider

My little "retirement home" is 1970's modular ranch which had a 3/4 inch subfloor topped with a 3/4 inch particle board underlayment. Except for the kitchen and bath, it was all carpeted. I ripped out the carpet in the living room, dining area and hallway. and put down 3/4 inch hardwood in the living room, dining area and hall and installed porcelain tile in the kitchen and bath over cement board underlayment. So far the bedrooms are still carpeted. So my reworked floors are 2 1/4" thick. I installed 7/8 pex from Radiant Floor Company on 16" centers with aluminum plates, circulating 140* max water and I've never been more comfortable. Minimum usable water temp is about 100*. My room temp. does overshoot a little because of the mass of the floor. The circulators don't cycle as often as they would with a lower mass floor. I keep the thermostats at 70* and the room will cycle from 69* to a little over 70*. I must add that the house is very tight and very well insulated.

As for your concern about high ceilings or cathedral ceilings, I did some work on an architect designed ski home at a local ski resort which had a ceiling height of about thirty two feet on half of the home the other half contained the upstairs bedrooms coming off a mezzanine walkway that was within the high ceiling area. Their theory was that the radiant floor was only effective up 'till 7 or 8 feet and in order to be comfortable above that height on the mezzanine, they incorporated some kick space heaters into some built-in benches on the lower level. In other words, according to their thinking, your space with high ceilings should be comfortable with radiant if you don't need heat above 7 feet.

 

[coolidge]

The floor is a 1" subfloor and 3/4" oak and pine. I have about a 400 sq ft crawlspace that i will be running radiant in also. Now in the dining, kitchen, common area( 24 x 36) with half of that crawl space, there is about 16 ft of baseboard. Not hardly enough to heat that area. With two other rooms ( 12x24) with wall to wall baseboard, on foundation. No heat at all on second floor. Basement walls have been sprayfoamed to tighten it up( HUGE difference). As i said i am slowly ripping out the exterior walls and replacing the insulation. So i should see if i can get an energy audit done to see what the heat loss is for the first floor.

 

[Sting]

I also should say that I have a strong bias against panels in most living spaces because I don't like giving up the wall real estate for them, not to mention that IMHO they are *UGLY* so I'd really want to try hard to avoid them.

Gooserider

Agreed hands down I prefer the look of an old cast radiator, freshly sandblasted and repainted to an automotive finish -- but that's just me!

In the recent "rehabbing" (circa 1906) project, a good deal of the old horse hair plaster is either beyond salvage or needed to be removed to provide chases for upgrades to floors above. In all cases, I had a sub shim the full cut studs back to trim finish depth (using metal studs that are straight) to allow installation of modern 1/2 drywall (without disturbing the old trim) then I had panels roughed into the stud bays to support staple up tubing with radiant foil to direct the energy back at the new finished wall. This has worked great to keep north and west facing room exposures draft free and comfortable -- yet the room shows no sign of modern heating incursions when finished. In a bathroom -- where there wasn't enough floor or wall space -- I did this in the ceiling also. That room is kept at 72 during the heating season and the owner says its a pleasure to step OUT of the shower when its cold outdoors.

Just an idea -- depends on how much of a project want or the customer can pay for!

 

[Sting]

one point regarding insulating on the inside of basement walls in very cold climates.....(Wisconsin -- Maine etc) Once those old foundation walls are allowed to go cold because energy is no longer available to keep the frost out of structure and near soil , they will never sustain the frost penetration and they will crumble in years to come. If you dig around the outside and provide a frost barrier of at least 2 inch foam board with modern drainage, you then can safely place a moisture barrier and finish the inside surface.

Now since most folks live at one location for only a few years -- its not a problem for the current occupant -- maybe not the next - but soon enough someone will be jacking up the house to put a new basement under it!

Kind Regards
Sting

 

[tom in maine]

I would suggest a couple thoughts on insulating basements.
Southern building codes are concerned about exterior insulation creating a pathway for termites and carpenter ants getting up into the house.
If you insulate on the exterior, I think there is some prudence in starting at the footing and only insulating to grade on the exterior.
You can then insulate on the inside from the sill down a couple feet below grade. This is not perfect, but it eliminated the critter problem, which can also occur up here in the northern states and it still cuts the heat loss.

I have used spray foam on the interior and believe that the only time there will be damage to the walls is when you are in an area of bad soils (expansive soils, ie, clay or soils that hold a water). In well drained soils, you can insulate on the interior from the footer to the sills.

Tom in Maine

 

[SolarAndWood]

I had panels roughed into the stud bays to support staple up tubing with radiant foil to direct the energy back at the new finished wall.

How big is the wall cavity? Is this the only heat source in the room? I assume you would need to frame an inner wall if all you have is a 2x6 exterior wall?

I have a 50x22 room with 50 feet of glass and just under 10 foot ceilings. I am currently thinking that I will need baseboards in addition to the floor to keep it warm. However, maybe tubing in the walls and ceiling would do it.

 

[pybyr]

I would suggest a couple thoughts on insulating basements.
Southern building codes are concerned about exterior insulation creating a pathway for termites and carpenter ants getting up into the house.
If you insulate on the exterior, I think there is some prudence in starting at the footing and only insulating to grade on the exterior.
You can then insulate on the inside from the sill down a couple feet below grade. This is not perfect, but it eliminated the critter problem, which can also occur up here in the northern states and it still cuts the heat loss.

I have used spray foam on the interior and believe that the only time there will be damage to the walls is when you are in an area of bad soils (expansive soils, ie, clay or soils that hold a water). In well drained soils, you can insulate on the interior from the footer to the sills.

Tom in Maine

I generally agree with your points, Tom (and always value your contributions around here) (and I think the inside/ outside insulation technique you mention makes the most sense in the widest range of situations) but in my opinion (after looking into it a lot with/ for my 1840+/- house with mostly original foundation) there are some additional variables beyond soil type/ drainage:

A modern-type poured concrete/ steel reinforced foundation can take a lot if the drainage is OK. An older non-steel reinforced cement foundation can crack a lot more easily if the foundation gets cold and the frost works down in (I've seen this in turn-of-the 20th century houses in well drained locations in sandy soil but in cold climates) (and pre-WWII cement and concrete varied a lot more than modern concrete in terms of both material contents and the skills of the installers). Brick or cement block foundations are weaker still. Cinderblock foundations are even weaker from frost/ soil movement, because the blocks themselves are less robust (and more prone to taking on moisture and then spalling from freezing) than concrete blocks. Mortared or unmortatered hand-laid local stone foundations really do poorly- fast- if the foundation and adjoining soil are allowed to freeze and expand/ contract.

I've got one of those hand-laid unmortared foundations (from ground level down, with large granite curbing from ground level up to the sills) and after looking into it and talking to some experienced and scrupulous insulation pros, I'd _never_ insulate it too deep on the inside. I am all for saving energy, but it'd take a lot of energy savings to pay for a new foundation- but I have made some significant progress simply by beginning to work on sealing voids between the stone were cold air is/ was leaking in.

 

[SolarAndWood]

cold glass will sweat from warm air in room i think. consider baseboard under glass wall to avert condensation on glass.

Agreed, in floor with a line of baseboards under the glass is the current plan. That and some kind of insulated blinds that drop out of a soffit. The stove runs wide open to keep up when it is cold and the wind is blowing.

 

[heaterman]

"staple up radiant floor w/ aluminum plates is supposed to be good for about 40 BTU / Hr / sq. foot, and if that works from a numbers standpoint, I don’t know why it wouldn’t make for a comfortable room…"

This is achievable but to get 40btu/sq ft usually means a surface temp of at least the mid 90* range or higher depending on room ambient temp.. At which point your warm floor will become a somewhat uncomfortable hot floor when standing in one place even for a short period of time. I've found that a design range of no more than 25-30 is best from a comfort standpoint. Anything past that and I use something to supplement. Lot's of times especially in new construction, I'll run into the situation where the whole house will heat with 15-17 btu/sq ft except for one room which may need 25-30. In that case I'll use something to supplement that room rather than going with a 2 temp system.
Now............if you want to think outside the box and go for 40-50 btu/sq ft., use your walls. They can be driven about as high as you would even need and not cause discomfort. The above mentioned Viega Climate panel works great underneath a layer of drywall. The homeowners just have to remember not to hang any pictures in the tubed areas.