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Radiant in a school

My company is designing the MEP/FP services for a campus style high school in suburban Boston. I am the HVAC engineer for the team, and am a big fan of condensing boilers, radiant heat, and wringing BTU's from stones if possible.

The proposed scenario is to build new over a now-open area, move the occupants in, demolish the existing and build the second phase. The current boiler plant (two actually) are oil fired cast iron 180F hot water. This will be retained during demolition to serve the new construction temporarily then the campus would be switched over to a new plant so the old can be demolished. New plant may be gas (TBD) or naturally, #2 oil as they have now.

Here is my question:
With so much slab on grade, radiant slabs become an obvious choice to maximize overall fuel efficiency not to mention comfort. But any school and committee in particular often have skeptics that rightly ask: "What about leaks? What if??.."

Inevitably there will be some glitch, an errant nail what have you that would be red meat to the skeptics.

So it gets down to warranty I suppose, but also track record and "commonality" of this application in a school.

How would you go about selling this, assuring an owner paying for a 50-year lifecycle building that they will not be ripping up their floors after the common 25-year warranty period that some PEX manufacturers offer?
And would PEX-AL-PEX be a better choice for durability?

If it were my house, I would not hesitate and I can say that because it is my own risk. But from a standpoint of professional liability as well as winning over converts to what we hope will be a model Green Design school, I put this forth for those of you that have installed more than I would ever design. Ideas?



  • dconnors
    dconnors Member Posts: 215
    my thoughts

    I would prefer Pex-Al-Pex. Check out the new Buderus SB boilers. We love really low return temps. Or call 1-800-Buderus and I will discuss this with you.
  • Paul Pollets
    Paul Pollets Member Posts: 3,616
    Condensing loads

    Brad, tubing puncture is very rare by errant tradesmen, and CAD loop layouts usually eliminate any threat. In a worse case scenario, any tubing damage can be repaired easily with a splice kit. Not to heat the slab with a radiant application would be wasteful of energy. My heating plant of choice would be a Viessmann Vertomat system and you should be speaking with Viessmann directly for engineering consult (call Ed Nordstrom at 1-800-288-0667) For the radiant application, speak with Tim Doran at Wirsbo 800-321-4739. There's an excellent article gracing the cover of this month's PMMag regarding schools replacing their systems with high tech boilers...see:

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  • Weezbo
    Weezbo Member Posts: 6,232
    Brad.....good clip...

    i would make a stipulation that there is to be no other workmen wandering about during your rough-in of the heating pipes ...it is problems a plenty just keeping an eye on the work your doing with out the added hassel of distractions from other tradesmen ...just do your work right be there during the pour...couples on the ready:)..best wishes and good luck with it.
  • hr
    hr Member Posts: 6,106
    I like your thinking

    to incorporate radiant. You may still have to address IAQ and air changes, etc. Probably still need some ducted system to cover this and AC loads.

    Public spaces where occupance loads change can be a bit tricky to control. I'd surely use some reset control to prevent slab overshooting.

    hot rod

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  • Brad White_2
    Brad White_2 Member Posts: 188
    No question on the ventilation, Hot Rod

    that will be a separate system entirely (AND will use low temperature water, of course!) We have to meet a minimum CFM of outside air per person and will use heat recovery wheels on exhaust. AC is yet another system, usually reserved by budget for administrative areas that are not only interior but work the summer too.

    It is the base level of heating that concerns us, how best to distribute it. Radiant gets the vote, it is convincing the somewhat conservative (read: cautious) board members. Mind you some are Gung-Ho on the latest and are sophisticated higher income folks who may have radiant in their homes now. That would help.

    I can see all this being Value-Engineered out. (Value Engineering is Neither.-BEW)

  • Brad White_2
    Brad White_2 Member Posts: 188
    If I could flat spec

    a boiler I would start with Viessmann Vertomats. I have specified them on private work but in public work here in MA we need to list three names. So Viessmann can compete because they have larger sizes requiring fewer boilers and hook-ups. Otherwise I specify Aerco Benchmark models or Lochinvar Intelli-Fin. Similar but different. Any other names you might suggest in the 2 million input range?
  • Brad White_2
    Brad White_2 Member Posts: 188
    Thanks Dave

    I have the same feeling, something about a metallic component in there. Is cost a major factor and does more than one manufacturer make it?

    We agree on low return temps. My design preference is to use 140F supply water on the coldest day and modulate down to 80F return water on a 55 degree day, which usually corresponds to 100F supply water.

    How big do Buderus go? The school will be about 260,000 SF and about 18.2 million BTU's, so I am looking at about six or seven Vertomats if Viessmann is in the mix, and maybe ten to twelve 2.0 million BTU Aerco, Lochinvars or others. Again, we may be limited to #2 oil, but I am required to foster competition.
  • dconnors
    dconnors Member Posts: 215

    We go to 4 million btu. Also would suggest R2107 controls. You can view all of this at www.buderus.net or give us a call.
    PS We do have case histories on schools available.
  • dconnors
    dconnors Member Posts: 215
    Do you need more info?

    If you need more engineering data please call us at Buderus
  • Paul Pollets
    Paul Pollets Member Posts: 3,616

    I'd be using a staged design, with at least 2-4 boilers. The Vertomat has the Dekamatic control, which can be customized. If I was using other boilers, I'd be staging with the Tekmar 264 control, depending upon application or need to integrate with building management software. The Danfos ECL can also stage multiple boilers.

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  • kr
    kr Member Posts: 2
    Contact this guy.

    Does lots of radiant design in and around Boston.

    Jeff Dirksen
    Emerson Swan
  • Radiant in schools.

    As a school custodian, I would be concerned about overheating w/ a radiant slab in a classroom. Especially in
    the spring & fall w/ cool nights & warm-hot days. The southern exposure rooms in my building can get hot on those days. With a warm slab & lots of active, heat producing bodies, you are asking for overheating complaints, IMO. Maybe if you only heated w/ the HVAC system, until a certain low outside temp. was reached before turning on the radiant? Even then it would have to be throttled down to prevent overheating.
  • tim smith
    tim smith Member Posts: 2,544
    school heat, see attatchment also

    Wild idea, don't know how it will pencil but here goes. What about steel wall panels on exterior walls, oversized for lower temps, also run some wider centers radiant in slab. Panels could be sized to where if there was ever a problem with tube the temp could be ramped up to heat the spaces with panels. could also hit panel first with a bit higher temps and then return through floor to bring down return temps. Just a rough idea but food for thought. Would think less tube might partially offset the panel costs. Also would not have separate piping costs for panel if you fed back through radiant slab.
  • George_10
    George_10 Member Posts: 580
    Do your client a favor and spec

    in cleaning and treatment of the system before putting into service. This will be a large dollar purchase no matter what components are used and the water treatment would be insurance that you eliminate water chemical problems from developing. Also because scale and corrosion are kept under control, the design efficiency will be maintained.

    This pay back in efficient operation will show up in lower fuel bills. A win-win situation for your client. Problem prevention and lower fuel bills.

    Our web site has further details under hydronic products.


  • there are many ways to address that. proper zoning, feedback/reset control, slab temperature monitoring, added heat in the vent...

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  • Brad White_2
    Brad White_2 Member Posts: 188
    Jeff is

    one of my favorite vendors!
  • Brad White_2
    Brad White_2 Member Posts: 188
    Being a customer of yours

    George, I know whereof you speak. Still, I need three names in this state for public work, but the cleaning point is always well taken.
  • Brad White_2
    Brad White_2 Member Posts: 188
    Controls would be key

    to this Dennis. Absolutely. That you are on the leading edge means more to your comments. We would anticipate a shake-out period of adjustments with all of the slabs. We may limit radiant to common areas not classrooms or go lightly as a base level of heat. Thermal flywheel is an issue. Thanks
  • green building

    How about putting solar panels on the roof and having a seperate radiant heating system. What town near Boston are you building in? Bob

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  • Brad White_2
    Brad White_2 Member Posts: 188
    I could tell you, Bob

    but then I would have to, well, y'know. Being preliminary, I cannot reveal too much detail for it affects competition. You could probably figure it out, though!

    No offense, just following policy and professional canon of ethics, I know you understand.
This discussion has been closed.