Retrofitting a small home in CT
Last Post 06 Oct 2008 09:49 AM by NRT.Rob. 3 Replies.
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chris37User is Offline
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03 Oct 2008 12:09 PM
Hi everyone,

I'm renovating a small house (935 sf) in central CT and would like to put in radiant heat. Since this is an older home that has undergone a number of additions there are a few problems that I'm hoping someone can help solve.

First, the original building (400sf) has doubled 2x4 joist construction. This seems to me too small for any hole or notch to accommodate tubing. So I'm thinking of baseboard in this area (bedrooms, bathrm) -- as I understand it, a single heating unit could heat both baseboard and underfloor tubing but the baseboard would need a higher temp. Is that right? or can baseboard be run at the same low temp as underfloor tubing?

second, I have only 1 flue in my chimney and I recently purchased a woodstove fireplace insert. So any water heater/boiler needs to be one that can be vented via PVC.

I calculated the heat loss to be 25,000 Btu/hr. I believe CT has 6000 degree days.

I've been reading some of the past postings -- a mod/con boiler w/an indirect water heater (Trinity, Viessman, Munchkin, etc) sounds ideal but would a high-efficiency water heater (Polaris, Navien) be a better fit?

I'm taking architecture classes part-time and find the heating field very challenging to understand -- but I'm trying.

THanks for any help!
Chris
quailrunnerUser is Offline
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04 Oct 2008 08:35 PM
This just a guess, but from what I've read here and other places, the space you are heating is not large enough to justify a mod/con - a good hot water heater is likely to do as well.
BadgerBoilerMNUser is Offline
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06 Oct 2008 08:10 AM
European panel radiators instead of baseboard and radiant sub-floor where possible on different zones with Bradford White's Combi II water heater with domestic hot water. Perfection. A Munchkin will work nicely but the Navien and Polaris cost more and are not made for space heating. You should have a design and get a professional to help.
MA<br>www.badgerboilerservice.com
NRT.RobUser is Offline
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06 Oct 2008 09:49 AM
In connecticut, your design temp can easily be about zero degrees. If your max load at zero is 25kBTUs/hr, thats about 8600 BTUs/degree day at 100% efficiency. Figure a 0.7 Multiplier on degree days for days that occur outside of the normal heating season.

I normally assume a 75% efficiency or so for a tank water heater (not the polaris). that's about 48.2 million BTUs/year for heating or so, max, with a water heater. at 94kbTUs/gallon of natural gas, that's about 515 gallons of natural gas or so.

A mod con (preferably a Prestige Solo to reduce cycling or Excellence for low rate DHW as well) at low temp (95% efficiency, roughly) gets you down to about 400 gallons of natural gas/year.

this does not take into account domestic hot water efficiency increases.

so, at a savings of about 100 gallons of natural gas a year, you can calculate payback if you know your gas price and price of the options are you are looking at.
Rockport Mechanical<br>RockportMechanical.com
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