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  1. #1
    Join Date
    Feb 2010
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    3

    Exclamation Hydronic Radiant Heat

    I am planning an addition to my house and considering hydronic radiant heat floors as the only option for heating the new addition and some existing areas like bath. I have problems finding any knowledgeable HVAC contractor who has experience in hydronic heat and can give me an unbiased honest advice and help me design the system.

    I spent quite a time researching the subject ****** but got completely different opinions. I would really appreciate if someone with the knowledge would tell me, what heat source is preferred in my case and what the whole system consists of.

    The addition is ~1500sf, I live in central NJ, the fuel is NG. Current heating is forced air furnace, I do not want to touch it, new system will be an addition, not replacement. The addition will include big room on slab foundation and second story area. The house will be well insulated: all attics R-49, walls R-19.5, floors under second story addition will be probably R-30 and the slab will have at least 2" (R-13) foam insulation. All windows are E4 Andersen windows.

    I want at least two zone hydronic system for new addition: one is for big room on the slab and another for second story area. I intend embedding PEX tubes into the slab, tired them to rebar, and for second story with hardwood floors I will put plywood panels with grooves and aluminum backing and run the PEX tube inside the grooves.

    I have very limited space in my basement where new system can be installed. So the ideal approach for me for the heat source would be radiant heat source and water heater combination unit that does not take much floor space. This unit will also replace existing NG water heater and provide hot water for entire house. Especial value for me would be the system that I can at least partially DIY.

    Any advice would be greatly appreciated.

  2. #2
    Join Date
    Feb 2008
    Posts
    550

    Default Re: Hydronic Radiant Heat

    isog02:

    From your post, you seem to have a very good idea of what radiant system you want.

    Count it as advantages that you have natural gas & live in NJ---there are more likely to be available knowledgeable radiant installers, if you look hard enough.

    Any radiant installer of course would have to wait until the addition was actually built, unless they were directly involved in the placing of the slab PEX---this may be the reason many of them won't get involved until the addition is actually in place.

    The inception & base of the plan is based on the installer doing a Manual J HEAT LOSS CALCULATION on the addition to determine how many BTUs/hour are needed to keep the addition warm--a very rough, basic calc would allow 30-35 BTU/HR per sq. foot of addition: 1500 X 35 = 52,500 BTU/HR needed to heat the space & the size of the boiler---but this number could be as low as 45k BTU/HR---it's just a guess.

    Radiant heat is more complicated than other forms of hydronic---there are thousands of feet of PEX to install along with zone valves, circulation pumps, and other components that involve hydronic heat---expansion tank, Spirovent, check valves, low water cutoff, backflow preventer, purging station (to get the air out), the list is long & labor intensive---it's absolutely essential that you hire someone who's done it many times before---it can be very tricky to get it right the first time---there are a lot of bugs to iron out if the installer doesn't know what he's doing----that's why radiant tends to cost in the $10k to $15k price range.

    Special attention has to be paid to installing PEX in perimeter locations around and abutting outside walls---this area is very uncomfortable if extra PEX is not installed there.

    Consult the Yellow Pages under Heating Contractors & check the display ads to see if any of them say they specialize in radiant; also, in the YP, check out "Heating-Parts" to get the list of plumbing/heating supply houses in your area--go in to talk to the counterman (in the afternoon when it's not busy) & ask for several recommendations of radiant installers in your area.

    Condensing boilers are widely used for radiant installs--a good one is Triangle Tube Prestige Solo, which is gas-fired, condensing, but there are numerous other condensing boilers available, as well---This is a wall-hung unit that will save floor space--I would combine it with the Triangle Tube Smart 40 indirect hot water heater---an ****** price quote can be seen at Pex Supply, below.

    Radiant operates at 120 degrees water temp & has a much slower response to temp change than standard heating systems (180 degrees for standard HW systems)---therefore, the circulator is running most of the time with an outdoor reset to keep pumping ths 120 degree water thru the system---the idea is to "pump" as many BTUs as possible into the floor slab or wood floor structure (both of which are used as a gigantic radiator to keep the building temp around 68 degrees.

    It's a tedious process, but keep looking for the right installer--it takes time, but you'll be rewarded with the satisfaction of getting a great heating system at the lowest price you can negotiate.



    http://www.pexsupply.com
    http://www.patriot-supply.com
    http://www.houseneeds.com/shop/atop/...atingindex.asp
    Last edited by NashuaTech; 02-07-2010 at 05:25 PM.

  3. #3
    Join Date
    Feb 2010
    Posts
    3

    Default Re: Hydronic Radiant Heat

    Quote Originally Posted by NashuaTech View Post
    isog02:

    From your post, you seem to have a very good idea of what radiant system you want.

    Count it as advantages that you have natural gas & live in NJ---there are more likely to be available knowledgeable radiant installers, if you look hard enough.

    Any radiant installer of course would have to wait until the addition was actually built, unless they were directly involved in the placing of the slab PEX---this may be the reason many of them won't get involved until the addition is actually in place.

    The inception & base of the plan is based on the installer doing a Manual J HEAT LOSS CALCULATION on the addition to determine how many BTUs/hour are needed to keep the addition warm--a very rough, basic calc would allow 30-35 BTU/HR per sq. foot of addition: 1500 X 35 = 52,500 BTU/HR needed to heat the space & the size of the boiler---but this number could be as low as 45k BTU/HR---it's just a guess.

    Radiant heat is more complicated than other forms of hydronic---there are thousands of feet of PEX to install along with zone valves, circulation pumps, and other components that involve hydronic heat---expansion tank, Spirovent, check valves, low water cutoff, backflow preventer, purging station (to get the air out), the list is long & labor intensive---it's absolutely essential that you hire someone who's done it many times before---it can be very tricky to get it right the first time---there are a lot of bugs to iron out if the installer doesn't know what he's doing----that's why radiant tends to cost in the $10k to $15k price range.

    Special attention has to be paid to installing PEX in perimeter locations around and abutting outside walls---this area is very uncomfortable if extra PEX is not installed there.

    Consult the Yellow Pages under Heating Contractors & check the display ads to see if any of them say they specialize in radiant; also, in the YP, check out "Heating-Parts" to get the list of plumbing/heating supply houses in your area--go in to talk to the counterman (in the afternoon when it's not busy) & ask for several recommendations of radiant installers in your area.

    Condensing boilers are widely used for radiant installs--a good one is Triangle Tube Prestige Solo, which is gas-fired, condensing, but there are numerous other condensing boilers available, as well---This is a wall-hung unit that will save floor space--I would combine it with the Triangle Tube Smart 40 indirect hot water heater---an ****** price quote can be seen at Pex Supply, below.

    Radiant operates at 120 degrees water temp & has a much slower response to temp change than standard heating systems (180 degrees for standard HW systems)---therefore, the circulator is running most of the time with an outdoor reset to keep pumping ths 120 degree water thru the system---the idea is to "pump" as many BTUs as possible into the floor slab or wood floor structure (both of which are used as a gigantic radiator to keep the building temp around 68 degrees.

    It's a tedious process, but keep looking for the right installer--it takes time, but you'll be rewarded with the satisfaction of getting a great heating system at the lowest price you can negotiate.



    http://www.pexsupply.com
    http://www.patriot-supply.com
    http://www.houseneeds.com/shop/atop/...atingindex.asp
    Thank you very much for your response. I do not understand why radiant heat designer needs to wait until the addition is done. I am not looking at this stage at installation. I am looking for a professional design that takes into consideration my house specifics.

    I understand the cost of the whole system is very high both in labor and parts. I hope to lower labor cost by doing some of installing myself having good detailed design. I hope I will be able to tie PEX tubing to rebar in the slab, routing grooves in plywood to install over second story addition subfloor and running PEX tubes inside these grooves. I can possibly install manifolds and other components of the system. Thatís why I need very good design that would spell all details.

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