basement fun: radiant electric heat, self-leveling compounds, indirect water heaters

jeffro83 · June 2011

Hey there. New user here, though I've followed the forums for a while. I'm currently undertaking a basement project that's going to take up all of my spare time from now until the end of days...give or take a few.

Just curious if anyone has had a similar situation, or could give some advice.

My scenario:

-100+ yr old house, poured concrete slab, with about 20sq ft of dirt exposed at the highest/uphill side of it...just dug up the area to see what was there, and it appears to be a shallow drain or weeping tile, which eventually is coupled w/ an ABS pipe, looks like from what kind of materials are used, that it's last been dealt with 20~ yrs ago

-fairly heavily sloped from one end to the other (with little drainage tracks left whenever the basement was poured, all leading to the main floor drain), it's generally uneven in spots, but not EVERYwhere

-planning on having the most uphill side (I know, that sounds terrible) of the basement as a bedroom (the area with dirt at the highest point), which also has the most slope of the basement...over the 13ft or so (from the insulated wall to the closest part of the yellow extension cord in the picture), there's about a 2.5-3" difference in height from the dirt side to where the room will end

-as I don't have much clearance height in this old basement, I'm trying to save as much headroom as possible when filling in this gap

I've got delta FL that i'll be using on top of the slab as a vapor barrier, and I plan to put self-leveling compound on top of that, which i'll be setting a radiant electric heating cable system inside of....obviously if I'm dealing with 3" of slope over 13ft, that's a heck of a lot of SLC. Should I just use mix & pour concrete to fill in the dirt part (digging the dirt out to at least the depth of the concrete beside it) and then level, also w/ mix & pour concrete to roughly the 2" height at the lowest part of where the room will end, and then put down the delta FL & SLC over the Delta? Also, I planned to do the same thing with the bathroom side (the left side of the picture), though the slope is not nearly as bad as the bedroom side.

Also, just a quick question about indirect hot water heating...I've currently got a Buderus GB-142-30 (91,500btu) heating my 2.5 story house, and our current hot water heater for the 4 (adults) of us is a 60gal gas fired heater, that we only ever entirely use up if someone takes a Jacuzzi bath, and say runs the dishwasher at the same time. Was looking at a Triangle Tube Smart 40/50/60 setup, but I was told because they're so much more efficient in the way they heat water, that I wouldn't need nearly a 60gal indirect heater. Would a 40gal be way too small for our needs? One last question, can I get away with a cast iron circ pump for this indirect heater I'm looking to get? Or do I need steel/bronze, to avoid rust.

Any and all help is much appreciated, if you care to pipe up!!

STEVEusaPA · June 2011

well.....

I'll try to ask as many questions as I can.

1. First, I hope you checked your local codes regarding a bedroom in a basement. Many require an exterior egress window/door bigger then the one in the pic.

2. Ideally I would jackhammer the whole floor up, redo the drains, vapor barrier, insulate under the properly graded slab, and do some radiant tubing. A 100 yr old house probably only has 1.5 inches of concrete, so a small demo hammer would do the trick.

3. It's hard to tell, but I'm guessing it would not be a good idea to try to go from 3" to nothing with floor leveler. Thats alot of mixing. A better (costly) solution might be to make a 3 1/2 in curb on the low side, and have gypcrete pumped in, but you still have to deal with the drains. And if you're going to get a pump truck, I would go with #2.

Short of jack hammering, anything you do, I guess, would work.

I have a Smart 60. It doesnt appear to be oversized. They are well insulated, and dont have alot of standby loss (insulate pipes). Filling up a 4' X 6' tub and doing other 'how water things', I 've never ran out of hot water. Make sure the piping to and from the boiler is correct. I would use a boiler control with outdoor reset, and DHW priority, or even a Taco relay with priority.

Cast iron circ is fine for the circuit to/from the boiler, assuming you're not using a non-oxygen barrier pex in the system, or this circuit is separeted by a heat exchanger.

You could always get the floor as level as possible, and do some baseboard, or panel radiators.

I just think if you got a boiler, take advantage of all the modern technology.

Good luck

jeffro83 · June 2011

thanks!

thanks a bunch for your reply, steve.

1. to be entirely honest, i don't think my municipality has the strict egress window rules that most larger cities seem to have these days...i'm a service guy by trade, so i'm in 40-50 houses a week, and i've never once seen a proper egress window in a basement. safety second!...apparently.

2. i seriously thought about doing this for a long time, and most of the people i've sought advice from said from the outside, it might LOOK easy, but could end up being a nightmare because a) i stand a chance that my basement walls could start to cave in, and b) they figure because the way the basement currently looks; where the concrete seems to just stop...that there's most likely bedrock underneath that area (when i started digging up the dirt section i think i might have indeed hit bedrock). ideally, even with the added cost, if it were feasible, i'd love to just redo the slab, but i don't think it's in the cards...too many variables.

3. i hadn't really thought of that...but that would work too....any rough idea what gypcrete goes for, pricewise? granted, i know it'll vary everywhere.

i've mostly been eyeing up the smart50, and it seems like it would be fine for our needs...wouldn't the cast iron circ rust though? it's an open system, no?

STEVEusaPA · June 2011

your buderus

is a mod-con right? The circulator is for the piping from the boiler to the indirect. If you are using a DHW return loop with a circ, then yes a bronze circulator for the potable water.

Just to make sure we're on the same wavelength, The water from the boiler to the indirect, does not mix with your domestic, potable water. They are separated in your DHW tank (boiler water on the outside, domestic on the inside). Just make sure you have someone who knows how to pipe everything up, and you follow all the manufacturer's instructions, especially for the indirect (T&P relief valve, backflow preventer, etc).

This may help (pps 14-16).

http://www.buderus.us/files/201001211307550.72150200_GB142InstallationOperationEN.pdf

jeffro83 · June 2011

yes...

the buderus is a modulating/condensing boiler, and yes the boiler's grundfos ups15-58 circulates the water to my household rads, and when i pipe the boiler supply line into the indirect, it'll flow there as well...but i am under the assumption, the potable hot water from my indirect to the faucets needs to be pumped, and probably by a bronze/stainless pump...does it matter if the pump is installed before the cold water in, or on the hot water out?

and yes, you're right, the boiler's circulating water is definitely not in contact w/ the potable water (the whole 'tank in tank' idea, on the indirect).

i guess i've never been able to justify the whole 'instant hot water' idea, with a constantly recirculated hot water system...i just plan to replace the function of my rental gas fired hot water heater with the indirect, since i've got a high efficiency boiler that's average to small, considering my house size/usage.

STEVEusaPA · June 2011

yes bronze

Yes, bronze for your domestic hot water recirculation.

I don't know the cost for gypcrete, depends alot on your area and logistics.

There are a few ways to pipe your indirect, but I contstantly follow the install manual with the equipment, seems to never let me down. As far as the bronze circ, grunfos & taco both make systems for domestic hot water circulation. I would check them out to help you make a decision. They all have their deficiencies, I feel, and I'm currently trying something different in my own home (my personal experiment).

Second thoughts about heating your basement. If you have enough btu's (decided by a new complete heat loss), I would seriously consider abandoning the electric radiant. I just think it's not going to work. Think about putting heat on the floor (concrete, even bedrock, and that rock and possibly ground water sucking all that heat out of your basement. And once again, your going to do some repiping, and you got a very efficient boiler, reconsider some baseboard (even low temp), or some low temp panel radiators.

Just my 2 cents, 3 or 4 times

jeffro83 · June 2011

you're saying

baseboard hydronic instead of electric in-floor? meaning i'd still need to run piping or pex back to the boiler? what i was considering doing on top of the current slab (and on top of the delta FL vapor barrier) was laying an insulating layer of cork (around 1/8") before i put on the heating elements & SLC/concrete/gypcrete/etc. i just remember how much i've always hated baseboard heating, and how uneven it can be (compared to something in the floor itself).

if money and (more importantly) time weren't an issue, i'd gladly dig out my current slab, give myself 6" of additional headroom, pour a new slab with hydronic within it. however, i just don't see that happening. i plan to be done this project by september, and i'm mostly working on it solo.

but yes, i did consider my entire floor & slab could act as a giant heatsink, which was why i wanted to counter that with some insulating material below the heating element.

Bob Vennerbeck · June 2011

egress windows & to dig or not to dig....

While renovating an existing walkout basement apartment, we hemmed & hawed over whether to improve the egress from the back bedroom - it had a large hopper window near the ceiling. The next day, the local paper reported a mother and child died in a basement apartment fire where the windows had been sheetrocked over! We stopped wondering and ordered up an 'Escape Window' from http://www.escapewindows.net/ and two weeks later spent a long weekend carefully chiseling out concrete block and installing a pressure treated rough frame for it. Fairly hard work, not real cheap, but the Right Thing To Do, all within our own capabilities, and the room is a thousand times nicer to boot!

Digging - a half dozen houses or so I've found with radical bump-ups in basement floors - and so far they've all been "it must have been easier to stop digging and pour a thin rat-slab over the high spot - after all, it's just for storing coal and broken shovels"..

Of course, that means YOU will probably find granite a half-inch down, but if you're doing this yourself, and can find the time and energy, dig a test pit or two - easy enough to patch the floor, and you might find that the effort to do the work that previous occupants didn't think worthwhile will buy you a much nicer space than bringing it all UP to level.

Good luck

Vbob

STEVEusaPA · June 2011

jeffro,

Just offering my opinion. I'm sure you'll get some heat out of your proposed system. Consider what you're going to spend for the electric radiant, and more importantly what it will cost to run it, as opposed to what it would cost to adding a heating circuit from your very efficient boiler, and the operating cost of that, which I think would be very little. You could easily run some pex, or copper, over to the room, and use base or low temp panel radiators.

I've never heard of properly designed hydronic baseboard being uneven.

Good luck, happy remodeling.

basement fun: radiant electric heat, self-leveling compounds, indirect water heaters

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