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Adding carpet - Am I going to regret it?

DBB Member Posts: 3
I've had in-floor radiant heating installed for some 10 years while I've been finishing the construction of my house - and it's still not finished, but that's another story! I'm about to add carpeting finally and I'm worried that I'm going to drastically affect the performance of the system (ie higher costs). The question is - should I be concerned?

The house has 2000 sq ft of liveable area - just about half of that has tile and the other half will now have carpeting. Currently, I have been living with unfinished 1-1/2" concrete flooring with embedded tubing. I'll be getting a rubber pad for underneath the carpet and the carpet will have an R-Value of about 2.5 (polyester, about 3/4" thick).

The system has a 5 zone Tekmar 371 controller with injection pump. Up to this point, heating costs have been reasonable even though I'm located at 7500 ft in Colorado (because I use a wood burner stove) . Originally, the system was designed with the expectation of carpeting; however, I've gotten use to the low heating costs and am now afraid of the effects of the carpeting.

Does anyone have any words that will allay my concerns?

Thanks for your help!


  • Gordy
    Gordy Member Posts: 9,546

     IF the system was designed for carpeting, it should still perform well. But what r value carpet was the designer designing around?

    Most definitely your water temps in that part of the zone will need to be higher, which in turn will raise operating costs.

  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    My house has radiant in concrete slab.

    When I bought the house, the former owner left me with all the downstairs rooms carpeted except the kitchen and bathroom. All but the bathrom had about 1/8" thick asphalt tile on them.. The carpets had a foam rubber backing, not wall-to-wall but nearly. The were ugly, so I threw  most of them out. The foam had disintegrated, so it was a mess cleaning up. In the living room I put a 3/8 inch carpet on an underlay, also between 3/8 inch and 1/2 inch. I have no idea the R value of that stuff. The asphalt tiles had a layer of tar paper under them. I know this because the tiles in the kitchen started coming up, so I replace them with ceramic tile on top of a thin layer of sand (to even things out compared with the slightly wavy concrete.

    I do not know if the designer (if there was a designer) had anything in mind when he designed the heating system. I do not know the spacing, the design temperature, etc., he designed for. And the system had no thermometers except for the tridicator in the boiler. It ran between 130F and 140F. It mixed some of the return water with the boiler water to get back to the floor, so the floor ran at less than the boiler temperature. Mixing was with a manual globe valve. Anyhow, this was plenty to heat my house here in New Jersey where design temperature is 14F.

    My new boiler is a mod-con with outdoor reset and I run 75F to 120F into the floor, depending on outdoor temperature. It runs 112F on design day. And that is enough for my house. My upstairs zone is baseboard, so I run that hotter: 110F to 135F.
  • Gordy
    Gordy Member Posts: 9,546
    Change in response time

    One thing I forgot to mention your response time will not be as fast with the carpeting installed. This may be more prevalent to you, being that you have experienced the systems performance with out carpet.

  • DBB
    DBB Member Posts: 3
    Does this sound correct?

    Thanks for the responses.

    Gordy: The original heat loss assumed 1.39 for the R-value of carpet - I think that's a bit low.

    I decided to recreate the old heat loss calculation since I have a copy of Wirsbo's program (circa 2000). When I input all the data (carpet R-value of 3), it says the increase in total BTU/hr between what the flooring I have now is and adding the carpet is only about 5%. The water temps do increase significantly - from around 90 to 145. I'm concluding though, that my expenses will only go up 5%. Does that sound right? ......I would have thought it would have a greater impact.
  • Gordy
    Gordy Member Posts: 9,546
    managing carpeted area

    Is the area getting the carpet zoned separately? So when you raise the supply temps the tile does not receive the hotter temps.

    I would say 5% may be about right depends on what type of boiler you have, and how closely sized to the load it is. If its grossly over sized you may not notice anything but a longer response time.

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Hi ya Gordy...

    How are the women in your life doing these days? Well on the road to recovery I hope.

    Good to see you back here, pal.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Gordy
    Gordy Member Posts: 9,546
    edited October 2011

    They are getting better everyday! I will post an update in the main wall on a new thread with respect to the OP of this thread. Since the main wall is where I asked for everyones thoughts, and prayers.

This discussion has been closed.