Mixing radiant with forced air?

PG

Is this a big problem? Old part of the house has forced air, new addition is getting in floor radiant. Will I have any problems with zoning? Thanks

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Weezbo

would likely, work to your advantage.

are you suggesting supplemental heat and a return air?

PG

Not at all...........

I'm heating the addition with radiant and leaving th forced air in the old part of the house. One t-stat for forced air, 4 rooms in addition all zoned seperatly. Just wondering how the systems would co-exsist?

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Weezbo

well, it is something i haven done in over 20 years or so,

we use Hrv,s for some thing called IAQ ,indoor air quality is a bit of an issue these days and luckily for me we have been using them for decades. it should possibly be of interest in any newer construction. the placement of the existing duct work would probably have some relavancy and that is basically something that would be better determined by someone at the site. in the past i have had systems running with forced air and radiant however the people like the boiler heat so much they wanted the forced air outta there.I am going to say this will likely happen after you install the radiant. it may be zoned F/A and it may be balanced however,when people have a choise alot of them notice the differences and decide on the radiant.heat gains from the sun will likely benift from being removed from the radiant room and redistributed in other rooms of the home..this is why i say i think the balance of the two systems is some what advantageous. Larger commercial jobs i have done in the interim and we balance the air add cooling coils speed drive it blah bla bla in radiant heated buildings with outside snow melt. like to restate the inside air quality is becomming a more and more prevalent sniveling clause .

PG

Actually my concern was more about a room (or rooms) heated

with forced air drifting into the room(s) with radiant and shutting down the radiant or vica versa. I am not putting both types of heat in any one room. The old part of the house will have it's forced air and the new addition rooms will have radiant (no ducts being added).

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Weezbo

it is little bit tough ..sight unseen.....howsomever *~/:)

thats one heck of a long word for "forget everything negative and go with the flow a minit with me on this one........",i cannot see any problem...is the simple version.

Jack Smith

Answer

The answer is a definite maybe. There really are a lot of considerations which affect the answer. Size of addition, t stat placement, exposure direction, what size opening from addition to existing, what is current t stat setting as compared with radiant setting, and on, and on. We have had issues, but all were able to be remedied by stat location(putting them where we wanted them and not where they looked best aesthetically). We guarentee satisfaction on all our work, if your contractor doesn't, you have the wrong contractor, or you are interfering with his design.

PG

Man you sure get up early! Since I am a/the contractor........

I'll chew my butt out or fire me if I get it wrong. I'm just funnin with you. But yes I'm doing the work. We do lot's of steam and some hot water but since older areas that we service, very little radiant. But I love it, and want it, and trying not to miss a thing on my own install. Thanks

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Weezbo

You are going with a great idea ...

garage slabs have got to be the "Testing" ground for many of the people good at this stuff today. mostly because the car or pickup isnt going to snivel about obscure minor intangibles..........for the most part,keeping the t stat off the outside walls,out of direct line of fire in the kids indoor basketball hoop stuff like that still applies :)sun rooms are alot trickier place to get it right the first time, however dont worry ,just remember, insulate ventilate and heaterate oh and dont forget to get paid

hr

Yes,

there could be some disaggrement between the two controls. Will the addition be built that doors could close it from the other part of the home?

How do the heat load calcs on the addition size up to the exisiting space.

Heat travels to cold. Generally FA systems move the heat faster than radiant. It is possible the the FA system would kick on and heat the new space and not allow the slower responding radiant a chance to warm. The space may get warmed ok but not by the radiant.

If the new space is a concrete slab, that might not be desireable.

I'd calculate the old and new building heatloss, then see how the current equipment is sized, or oversized

What about cooling. Will the new addition have FA runs and a return to cool?

hot rod

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J.C.A._3

Just my .02

Depending on the placement of the radiant (slab/infloor , hardwood or staple-up) consider floor temp. sensors.

In anything poured or tiled, this would make the most sense. Find the temp. that everyone is most comfortable at and set it and forget it. Hopefully you'll be using a "smart enough boiler and control" to figure it out.

Using air sensors can be tricky, but not impossible. Remember that radiant heats everything, not just air. Air is a crappy transfer method and makes for wild temp. swings. Like Weezbo said...They'll be asking for it in the rest of the house soon after, so plan accordingly. Chris

PG

Thanks gentlemen! there will be doors, cooling all 2nd fl and

first floor addation. Floor sensors will be used, thinking about Triangle Tube Prestige boiler..what do you think? Want everything top top end, first class.........

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PG

And it is gypcrete oner crawl.



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rb_6

Landmines

In my experiance this diagram holds several solutions to landmines created when mixing radiant and air...can anyone catch the key points?

Weezbo

erh...I will take a look see......

i dont own the complete picture however the equal spacing the warmer pipe "conducting" a certain amount of btu's to the return,insulated ducts , an above groundheader that can be approached for purposeful and meaningful inter facing (way to get at the Thing)sealed plenums ,distribution of balanced duct work in bays that run in a space provided rather than chopped and whacked into the space across structural building members,at a depth as to keep new venilation holes from underminding the integrity of the system,and change the static pressure in the ducts,proper insulation to slow down the heat loss how am i doin so far>? place ment of tubing so as not to create undue noises throughout the home or in line or target area of floor joist,and away from edges that might get hit by a finish nail gun during the trim out.,designe of ceiling panels and floor panels to more equally distribute the btu's into a home ....and some nail plates to protect the tubing and a few preformed conduit bends as chanels into the panel space for the header fastened and wrapped with a insulation material to further facilitate any un forseen noise and the ability to motivate the tubing into more perfect alignement during installation of the headers...long enough tails to work with and not long enough to over heat an area with them....am i in the realm at least? ok somebolly els take a jot at it...

Don_61

Dont worry.

Hello Patrick..you should be fine.I have done this several
times and have discover that once the floor heats up,that in
most cases it will keep the forceair system in check if you will.

As Hotrod mention heat goes to cold,now think again what makes radiant heat a better choice over force air.

The forceair system is a fast responce system,and depending
on where the distribution system is install and most cases
in the attic or crawl.And in most cases they have a distribution system that leaks.

So if you have a neg in the force air area of the home,then where will all that radiant heat start to go?

hr

Ying and yang

drawing shows an attempt to insulate around the duct work? And some sort of red/blue counterflow piping against the joist?

Radiant ceiling and floors? Maybe some radiant in the wall where the red tubs feed down?

hot rod

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rb_6

Bing and Bang

The biggest landmines we've ever stepped on with air/water systems had to do with a GC failing to follow instructions and insulate/isolate the air from the radiant and distribution/radiant from the domestic cold water. (He "never had insulate on his other projects" was his words - so he ignored all the insulation details.)

In the first instance a long return duct was run under the heated floor to the extent that by the time the return air hit the face of the coil it needed cooling in the middle of winter. The temperature was uncontrollable and the only solution was to rip down the ceilings and insulate as per our drawings. The owner paid for warm floors so shutting the radiant off wasn't going to happen and since we need constant ventilation here in Canada, turning off the fans wasn't happening either so down came the ceilings, electrical, mechanical and duct work. We didn't have the inspection contract for that job but that was last time we agreed to let someone else take responsibility for this area. On the very same project uninsulated cold water lines shared the same space as uninsulated heating distribution lines for fan/coils, indoor pool heat exchangers and snow ice melt system...no need to tell the end of that story. Finally there were times that this project had both heating and cooling going on at the same time. The cooling ducts also shared the same space as large heating distribution lines increasing the cooling load...So the pretty cartoons we created essentially became a nice job site table cloth whilst the GC forged forward with blinders on...what’s the lyrics to oohlala..."I wish I knew then what I knew now."

hr

Bada bing! Very nice explanation, rb

and drawings!

I'm not clear on the original question, I thought he asked more about control issues regarding a FA thermostat and radiant zone.

This is the area I have had challanges with when the two are mixed in close proximity of each others controls.

Adding a small, especially sunroom, radiant to an exisiting FA heated home is probably the toughest control issue I have ever wrestled with.

hot rod

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PG

Exactly what my original question was about!



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hr

One suggestion

would be to bury a copper well in the middle if the slab pour. This allows you to use a dual air/ slab thermostat. I run copper or pex from the slab sensor well up to a junction box on the wall. This allows you to slip the thermistor down the tube, into the slab.

With this method, check out the tekmar 500 series. They allow slab min, max, set back ramp up, and a bunch of other cool features. Some models have two stage that might intergrate with your current system with some "imagineering"

It's the "too much of a good thing" challange with sunrooms. Without some sort of operatable shading they tend to over run the space when the sunshines.

You might just run a minimum slab temperature with the stat I mentioned and use some quick recovering panel radiators as the predominate heatsource.

This article has some insights.http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,4148,00.html

I'd love to hear Robert's thoughts! He has a knack for seeing a clear path over the next mountain

hot rod

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rb_6

Yes

You're right HR about the original question and sorry Patrick - can we call my rants and ramblings "a preventative side bar post"? Just in case a passionate but unintiated DIY'r reading the exchange thinks having a clover leaf of uninsulated pipes and ducts sharing the same cavity is acceptable...

Weezbo

I like the approach

indeed there can be vast differences in installation Techniques and minor technicalities arise from conversations over the telephone v.s. what is really going on Patrick , if you have a 26 foot high cathedral ceiling in the sun room with a fire place,open room off the mezzanine and open balcony off the second floor ,double glass to the enclosed garden at grade with the glass surrounding on three sides,and an enclosed stair way leading from it tho the starting room above the flat foof on the 16' high garage lad you are in over your head .if you are neglecting to mention these sort of details i can only think that you are being disingenuous in the questions your asking.in which case your better off entirely with hiring some qualified help to show up on the site and do his work right the first time.

PG

Weezbo.......tough love?

Nothing fancy here.......8'2" ceilings, double hung Pellas, doorwall. Pretty standard stuff. Sure one of my reps may help me. I appreciate the help and concerns but I will be doing this job. And it will be done right! Thanks

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