Good and budget friendly framed floor radiant option, above or below?

tbrooks

Hello all. Been awhile since I've been on here. Starting to move forward now with my project. The past week I poured footers, and have almost finished laying block on the addition. So I'm looking for the absolute cheapest way to run my pex, as my budget for my entire building project is not enough for a typical radiant system. I know I can't afford it now, but in the long run it will pay off. If I have to I may even throw in a woodstove to get me through next winter, until I can afford to finish the system.

I was planning on running pex under the floor, with extruded plates, but I've been trying to find some wallet friendly extruded plates, and thats not happening. Its looking like alot just for plates! Thats just insane to me, but I know I need them if I run under floor. Then I would also need to figure out what to do on the existing house with the wood blocking between the joists, and I have a girder dividing a few of my zones. I was thinking to remove the blocking completely and run a 2x4 t or l brace along the bottoms of the joists. I'm not sure if there is a better/more common way to do this on a retrofit. On the addition I will use metal blocking/bridging. The girder I would just have to work around.

But I have been thinking, maybe there is an above floor option that would be cheaper? I haven't looked into it much yet, but figured you guys would know. Right now the existing is 28x32, wide open, no structural interior walls (there will be interior walls later). The addition is 16x28, no interior walls, but most of the gable wall between the 2 will stay. I have never heard of gypcrete until looking into radiant, and have never seen it around here. I'm not sure if I can get it or how costly it would be, as I'm in a very rural area, and the nearest installer is likely an hour or more away (probably more). I have read somewhere about people ripping plywood strips, and running the pipe on top of the subfloor, but I'm not sure how efficient this would be without some sort of plates either.

Just hoping you guys can help me find the cheapest option possible. As I said I'm doing everything myself, and armed with the right info, I'm pretty capable of doing anything.

tbrooks

Oh and the existing floor joists are yellow pine, and are now undersized according to the new span tables (just barely), so I don't think it would be good to add the weight of gypcrete on top. Then again it could just be newer lumber that doesn't meet the new span tables. I could always add another girder in the center of the span though, if costs were that much different.

Rich_49

Look at http://www.sunboardpanel.com/Products.html . Found this to be the most cost friendly available and delivers better than it's higher priced counterparts . Graphite is quite an amazing material for energy transfer , research it .

After much mathing out of this and other products , you cannot buy the plywood , rip it , fasten it procure the aluminum and attach for anywhere near the cost of this . Jim S has a great product here and more may want to look into it .

Brewbeer

Tbrooks, I think your question should be worded "BEST wood framed floor option, above or below?"

tbrooks

Thanks rich, I'll look into that some more. Biggest problem I see is it is sold in NY, and I haven't found a price, but I will find out. I really don't mind the extra work of ripping and installing plywood, if it will save me money. I have looked a little into graphite, such as the rehau plates, but I find a lot of products are hard to find prices for, I guess the easiest route would just be to contact suppliers/manufacturers.

Brew, I was worried the wording on that may get me in trouble, but its the truth. I'm sure there are some incredible products out there, and I would love to have the best, however that is probably not in my budget. Actually the only heating system really in my budget is a wood stove lol, but it is my thought and feelings that the heating system is one of the most important aspects of the house.

I know anything above the sublfoor is better, since you lose the resistance of the subfloor. However, my system will only need to put out about 20k btu/h on design day with it installed underfloor. Therefore the small amount that I save long term going above the subfloor is really not as important to me as price to get things installed. I need to get this figured out, so I can better plan, and keep construction moving. Albeit, it is just me working, so its not like I'll be setting any records lol. If I went with nothing but the best, it would be years before I could afford to buy all my components, but I'm not going to just staple up flimsy plates underneath, as I know thats just a waste of my money and time.

Rich_49

@tbrooks
I hear what you're saying . You will not find pricing on the sunboard online , keeps away the riff raff from increasing prices , you know the supply chain parasites ! You can only get pricing from the manufacturer , this is a good thing .

If this is done right you can certainly use an HE water heater for the heat and hot water . Be careful though , many will mislead you and it may not be intentional . You can really leverage the mass of the right heater to bypass a boiler and alot of complexity and COST . Don't fall into the wall hung combi trap if you are looking for efficiency and lower first cost . Many here can help you , I would advise taking advantage of the first rate advice .

Brewbeer

@tbrooks "Best" implies a combination of what will work well, without being excessively costly. A lot of the pros here are very considerate of "overkilling" any particular problem, but they do want to make sure that what ever needs to be done, be done right the first time.

I would think an above floor system would be less costly since you could rip plywood into strips and use thinner gauge heat transfer plates than what would be needed in a staple up application.

tbrooks

Thank you guys. Rich if you remember I posted earlier this year about boilers. I am still hoping to be able to get an htp, but only time will tell. That is why I am here though, because of the good advice I received before, and to gain knowledge from those with experience. I have read Siggy's book once, and I am rereading again now, but it is just so much info to grasp, and alot of it won't even pertain to my system. Plus I just have so much going on in my head already. It is alot to think about when you are doing foundation, framing, heating, plumbing, electrical, cabinets, flooring, wall coverings, etc, etc, all by yourself. I do have the family to help, but for the most they are just unknowledgeable laborers. I know I will be on here alot when I actually start to "build" my system, as I will need lots of help.

@Brewbeer, I love to do things right the first time, and I am usually all for overkill, but I also know there are many situations where overkill can hurt, especially here. I wish I was in a better situation, to do things "better", as I would just build from scratch. But I must work with what I have, and turn this house into my home.

I did find this. Seems pretty simple. My only concern is having room for expansion? I could do this pretty quickly with a plan.
radiantec.com/pdf/Within_Subfloor_Installation_Radiant_Heat.pdf

Rich_49

Please tell me that is the only thing from Radiantec's site you are looking at ? Stay away from there and what they sell unless you're just looking at the aluminum and that idea .

tbrooks

Lol, I just googled radiant plywood strips and that came up

Brewbeer

@tbrooks The PDF you linked to was what I had in mind as it uses inexpensive plates and your (free) labor (and lots of it). I've given this method some thought as I dream of one day having radiant floors in my house. I'd try to get some feedback from the pros here about the expected output of a system like this.

The disadvantage to you of the above floor method is you need to do this now, before installing the finished floor. If funds are tight, you might be better off with installing a staple-up at some later date when you have more money to do so, but as you have discovered, the heavy gauge extruded aluminum plates are spendy. Consider designing it both ways and costing out both designs, and then decide if waiting is better for you.

Rich_49

Price out the plywood and the plates required . Compare to a product like Sunboard . Think about eliminating the possibility of losing a finger to save $78.89 and how many of the other tasks you can tackle with the extra time and all your fingers .

tbrooks

@Brewbeer actually its quite the opposite. If I were to do under floor, I wanted to put it in after my framing. My plan was complete framing, drill holes for plumbing and electric, and then install plates and pipe. That way I didn't have to work around wires and pipes, but would know where they were going. I will definitely be costing all options.

@Rich I've been running saws since I was 12, still got 10 fingers, at least most of them lol. I have and will continue to have much more time than I do money also lol. But a little extra costs would be well worth it. I requested a quote from them earlier, so we will find out. Either way, on top beats crawling around in the crawlspace trying to screw plates to the floor and run pipe.

Gordy

On top also gives a better product.

Rich_49

I hear ya . I had all my fingers till last October (2014) too . Stuff happens

tbrooks

That it does, slipped in mud yesterday and took a chunk out of my thumb on a concrete block of all things. I've done many stupid and dangerous things, but luckily I'm still intact. I even wear safety glasses nowadays (sometimes)

tbrooks

Well diy strips and plates is the very clear winner. @Rich I could almost save your number per sheet of plywood, with 28 sheets, that adds up quick. Also beats out extruded aluminum. Honestly I don't think it will take that much more work either.

tbrooks

Scratch that, slight miscalculation lol, its 42 sheets, but still a big savings

Dave H_2

tbrooks,

Looking at the numbers, 20k btus and 1344 sq.ft. you have almost 15 btu's per square foot.
That looks feasible for a suspended tube method depending upon the heat source and the finished floor assembly.
I have seen almost no difference in the comfort between underfloor or on top of the floor.
IMO, that would be the least expensive way to get radiant in into your project. The difference with using plates it typically a lower delivery temperature of about 30 degrees on a design day.

If your design water temperature with underfloor plates was around 120F, then without plates, you would need around 150F. Again this is on design days. If you use a modulating mixing strategy to control the water temperature, then the outdoor temperature rises that difference in design water temperature shrinks. Putting the tubing on top of the floor gets your supply water temp close to the underfloor with plates method. However a statement said earlier about below systems that the subfloor resistance is detrimental is not necessarily true. With a on-top system, the subfloor is still part of the assembly and will still get heated up.
When it comes down to it, make the radiant fit the house, don't make the house fit the radiant.

About the blocking installed, you could knock out whats there and replace with 2" shorter (ex, 2x10 blocking, replace with 2x8 and leave the gap at the top)

Yes the best of the best radiant floor system utilizes the lowest possible supply temp but sometimes gets superseded by the shear cost of the materials.

Now if the finished floor assembly starts to raise the design water temp, you can max out that temp and add supplemental heat when it gets really cold out (like that wood stove your were thinking about).

I've designed tons of systems that way for budget friendly radiant floor systems. The key thing is getting the radiant in!

Hope that helps.

Dave H.

SWEI

Dave H said:

a statement said earlier about below systems that the subfloor resistance is detrimental is not necessarily true. With a on-top system, the subfloor is still part of the assembly and will still get heated up.

The subfloor resistance will slow the response time, however. Outdoor reset control is pretty much mandatory with that configuration.

Gordy

@Dave H Why would I want to use higher awt to over come r value to deliver comfort that is recognized on top of the floor?

The goal should always be using the lowest possible awt to deliver the highest comfort level, 30* is huge especially if a mid/con is driving the system.

Bob Bona_4

Op said he wants "the absolute cheapest" pex install. Well, like Dave said, suspended is that. The fun is ensuring a consistent joist air gap new, and down the road, when insulating.

Gordy

Your right @Bob Bona cheap up front costs more in the long term. Suspended, and under floor radiant do have their place.

Bob Bona_4

Cringeworthy, but it's done

Brewbeer

With a staple up install, tbrooks could add the heavy extruded plates later in time when he can afford them (although the insulation removal and replacement doesn't sound like much fun). The wood stove is a good back up option if the staple up (without plates) doesn't cut it.

tbrooks

I didn't think there was a place for suspended pipe these days. To me its like having forced air just blowing into the crawlspace. I do want/need things as cheap as possible, but I'm not willing to sacrifice quality either. The main thing is being able to get my piping in so it doesn't delay progress and cost is big factor there. I think the diy strips will be my best bet, this helps with cost now as well, because I don't need to install any of it until I'm ready to install my flooring.

I'm not planning on a woodstove at any time really, unless it was just temporary. I will probably end up with elec or propane space heating until I can afford the rest of my system.

Gordy

I think that's a smart choice that keeps you moving forward with your project, in the end under or over can be done later.

tbrooks

Thank you guys, for your help and advice. I'm going back through my design, re-figuring for this and for the windows I picked out, and a few other changes. I will try and figure things out, but I'm sure I'll have lots of questions. I like having the advice of pros in the field, when I haven't done something before. It will be a good while before I will be installing though, I have a lot to do!

hot_rod

tbrooks said:

Thank you guys, for your help and advice. I'm going back through my design, re-figuring for this and for the windows I picked out, and a few other changes. I will try and figure things out, but I'm sure I'll have lots of questions. I like having the advice of pros in the field, when I haven't done something before. It will be a good while before I will be installing though, I have a lot to do!

If you do go with suspended tube, consider adding the UltraFins to it. I have a few UltraFin systems running with 130F supply temperatures. I used the ThermoFin around the high load area under the windows, the bare tube and UF everywhere else.

http://www.ultra-fin.com

BenWoj

Interesting read. I've had to remodel our house entirely when we first purchased it. Previous owner installed Radiant flooring in concrete with a boiler. Worked fine with the high water temp. Unfortunately, we had to redue all the floors after switching over to geothermal since the loops were to long for the pex size. The good news was that I got the chance to do a lot of research about radiant flooring since it needed to be efficient with lower water temps. We ended up installing a sandwich floors like you were talking about. Ripping plywood and then installing plates just below the flooring. I was a bit worried about it at first, but it's working amazing right now.

If you want to go cheaper on the plates, you could buy aluminum flashing at a hardware store and bend them yourself. I did that with my upstairs flooring. Saves $$, but you waist a lot more time installing and arguing with the wife.

tbrooks

Thanks, good to hear from someone that has done it. I don't think that I will try to make my plates. I work with flashing sometimes, and its a pita without a break. My only concern with running the pipe above floor, is transitioning the pipe down through the floor. I'm guessing you didn't have to deal with that as you had slab underneath. I know I prob shouldn't use 90s tho, as it will add to my head.

Dave H_2

The most important thing is the design and what it tells you for the designed water temperature whether or not to plate or not to plate.
If your design water temperature was around the 120 range without plates, adding plates gets you to 90 which is difficult to control and get the comfort you are looking for, which of course is warm floors.
Will it be more economical to operate? Sure, however in the long run when you compare it to the cost of the plates it will take a long time to recoup the difference.
Find out your design water temp before making the decision. I have plates and suspended in my own home and suspended works! you just need to know the numbers.
Another thought, just because the design water temp may be high (define high, its different for everyone), that water temp is only needed on design days. 2% of the heating season is at design day, the majority of the season is at half load where the target water temp will be much lower. Modulating the water temp will lower the water temp automatically getting the efficiency and comfort you are looking for.

Dave H

Gordy

@Dave H the expectation of warm floors in a radiant floor application was gone a long time ago. That is a bad sales pitch. Neutral is what should be expected in a well designed radiant floor system.

While I will agree there is room for a no plate, or suspended tube application in low load scenarios. I do not believe sacrificing to higher water temps as a part of design is an answer worth looking at. Especially if HE heat source is used. Study up there is higher efficiency at even lower water temps than 110*, not just below 130*.


Plates of a beer can variety while cheaper are not the answer either @BenWoj conduction is king in radiant design. Heavy gauge means a lot along with an omega style profile that wraps the tube snug. Poorly fitting plates to the tube detail is less than desirable. Remember your time is money, and making plates that are going to fit poorly to begin with when you could be installing good ones, and moving forward with your project.

Since the spirit of this thread is a cheap radiant floor I will say this. Over the top may add some plywood, but it is a much better product, and less labor intensive than crawling around in a crawl space drilling holes, and weaving, hanging tube on your back. Going under floor will only get you 15 btus SF. With much higher water temps than over the top. It takes little effort to rip plywood, and screw down sleeper fashion. Also much easier to lay tube and plates on top than trying to dodge wiring, and plumbing under the floor.

BenWoj

My living room ended up having to dip down in the floor to reach my manifolds below in the basement. In order to do that without bending them and causing a kink or have them constantly popping up, I made sure to put my holes from the top floor to the basement as parallel to my floor as possible. Once the tubing was in the basement I could deist and turn it where I need it to go.

tbrooks

Almost more of a slot than a hole... Thats what I was thinking

hot_rod

Make sure to chamfer the edge of the slot or it can kink the tube.

I took a long ship auger bit, drilled straight down, then slowly laid the drill down to the floor. It makes a nice gradual "slot" without the sharp edge that a sawed slot would.

That's how we dropped tubes out of the bottom of WarmBoard. A router works also, but slow and messy.

tbrooks

Thats exactly what i was thinking too. I have quite a few auger bits. Figured I would start cutting a 3/4x4" slot, and then use the auger to take the corners off.

hot_rod

You can skip the slot, drill straight down for the pilot hole, slowly lower the drill as it spins.

This way you chamfer both the top surface as well as the lower edge where the tube pops out. It makes a slick dual tapered slot, so to speak.

heathead

Hot Rod,

Great tip makes perfect sense. Easy and fast and effective.

Thanks