Designing Radiant Systems

somebody

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CaseNut

Radiant Heat Design -

I am aware that certain companies in the radiant heating business offer free design services. Here are my questions.

1. Is it possible for someone who has never visited and viewed a home, to perform an accurate heat loss survey based upon information provided to them? In other words, if they are told the layout of the house, the sizes/locations/quality of the windows/doors, the R-values of the insulation in walls/ceilings/floors, along with the location and orientation.......... are there any subtle nuances that would greatly affect the heat loss, that only an on-site inspection would reveal?

2. Have any of you used such services and if so, how well did your system turn out?

3. Have any of you Pros had a chance to view systems designed by these design services and if so, what was your assessment of the end result? Did you feel that the design was good, fair or bad? And if it was inadequate, what went wrong?

I am aware that all systems are only as good as the information input at the design stage but that must be followed up by first rate installation and finally, proper set-up.


All constructive comments are welcome.

Josh_10

Casenut, this is from a designers prospective... We "sell" our designs rather than give them away. To answer you first question it is possible to design without seeing the house. We do it all the time. However we need and accurate floor plan and yes a VERY detailed description of walls, windows, and doors. There is always some fudge factor to take care of the un-knowns but yes there are some.

2. I have heard of such services. They are provided by your local supply house. You buy their products and they will do a heat loss calc and if you're lucky a piping diagram. I have met some good supply house designers and some really bad ones. Do it at your own risk!!

3. I have seen good and bad supply house designs. One thing that is universal is if the installer has little experience there is no designer in the world that can anticipate that. I usually come in after the fact because it isn't working. I find blown transformers, backward zone valves, no differential pressur by-pass, pumps installed backward, wrong pipe diameters, air in the system because of lack of air purging understanding, etc.

Constantin

I'd check our NRT...

... Northeast Radiant in Gardiner, ME has many happy customers.

I believe that they can use blueprints, though I's spend the time and money also to hire a blower door on-site tester once the shell is up to ensure that the ACH are to plan. Perhaps Rob or Dave there will have time to elaborate on their services. A visit to their web site may also answer your questions.

Unknown

testing?

What are we being tested for?

Unknown

I am, of course, biased.

That said, first off you get what you pay for. If design is "free", well.. how much time and effort do you really think someone is spending on it? How much individual attention do you think this free project gets? It depends, but I would start from a place of skepticism.

Secondly, most designers, including on site ones, do their calculations and design work before the house is built, so we're all on the same footing there.. we're all making educated guesses about how things will go, making sure we have wiggle room in case we're wrong, etc etc.

The advantage of a local of equal design skill is that they know the area. A remote designer must know how different sites, or different climates may differ and affect their designs, and they must proactively ask questions if he or she is designing in an area they are not familiar with. Temperature swings, design temps, wind factors, etc.. these are things that can even vary site to site in the same area, you may even be in a "microclimate" without an ASHRAE logged weather station down the street. So the level of questioning you get from a potential remote designer I think is a pretty good indication of the level of consideration they are bringing to your project.

I think good installation diagrams, including tubing layouts and instructions, and good mechanical diagrams can really make the installation work well. But good diagrams aren't free IMHO. I've seen an awful lot of truly bad free designs in my time. I spend a significant amount of time cleaning up after them too.

I'll be the first to admit though, between two designers of equal skill, the local has an edge. Not the least of which is the possibility of a site visit.

hr

Shy away from

designs that just multiply the square footage of the home and use a good, better, best insulation and construction multiplier.

You really need a room by room heat load.

Also construction quality and site changes can factor heavily into a load design.

Ideally a design would be checked AFTER the home is framed.

Rare to see one match the blueprints exactly.

hot rod

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CaseNut

Thank you for the thoughtful and honest answers. I do agree that you get what you pay for so I will elaborate further.

Like many of you, I am a tradesman too. I have wired and plumbed complete homes and all of my work has passed inspections by the local authorities. As such, I find it difficult to sit by and pay someone else to perform work that I BELIEVE I am capable of doing, albeit, with some professional guidance. This is where some of you guys roll your eyes. LOL

But.... c'mon now. IF a designer comes up with a proper design and a spec sheet for the various pumps, valves etc etc, how difficult can it be to install the PEX into the joist cavities in accordance with the design layout? Yes, I am sure that you guys have seen some sloppy workmanship over the years by amateurs but I am a meticulous to a fault.

My next question is this.

Is it reasonable for me to approach a local firm that is expert in radiant heating and ask them for a quote on doing a heat loss, designing/spec'ing of the system and the final tune-up, thus leaving all the dog-work to me?

Have any of you participated in that type of installation? It would seem to me that the bulk of the labour costs for a complete radiant project (start to finish) would be in the actual installation of the various components.

Comments please.

CaseNut

Clarification

In reply to hotrod's post, I now see that it would be helpful to disclose that I am speaking about an existing stick-built bungalow, built in the mid-sixties. Currently, I am gutting the interior and throwing all the plaster, insulation, wiring and plumbing out the nearest window.

The exterior 2X4 framing is being furred out two more inches to allow R21.5 Roxul bats to be installed. As for the attic area, the existing insulation has been removed and will have two layers of Roxul R-21.5 batts running in cross-direction to each other.

Six mil poly vapour barrier will be installed on all ceilings and exterior wall surfaces prior to the addition of new drywall. Once the interior has been completed, the plan is to remove all the exterior brick in favour of a cement board board and batten panel system. All exterior walls will have two inch thick blue Dow Styro board fastened to it in order to help make up for the loss of the thickness of the brick. This will add another R-10 to the exterior for a potential R rating of 31.5.

The home sits on a conventional block basement wall system that is fully finished on the inside and is insulated with R-21.5 Roxul plus vapour barrier too.

hr

C-nut

maybe contact a local rep of radiant products. Many have training seminars for first timers. same for many of the wholesalers.

Most want to get you off on the right foot.

hot rod

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Paul Pollets

Training

I'd recommend the Uponor (Wirsbo) training in Apple Valley, Mn. Best in the business for radiant heating A-Z. including software design. You won't be sorry.

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hr

Wow, sound efficient

make sure all that data is cruched into the heat load calcs. An excellent example why not to use a one size fits all load multiplier!

Really efficient homes have some pitfalls when considering radiant. Low loads, say below 12 BTU/ square foot tend to not work the radiant enough. Possibly consider blending some panel radiators in sleeping areas and radiant floors for bath and kitchen areas.

Regardless you need a good "road map" to get there. AKA a heat load and design.

hot rod

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