Hydronic Heat Retrofit
We are renovating an Eichler style midcentury home in zone 6B. It’s a 2,700sq ft ranch with 1,000sq ft basement. Right now it’s using two furnaces 150,000btu and 90,000btu. Way oversized. For the sake of this conversation:
-Walls are currently 2×4 R8, we are retrofitting a double-stud wall with midwall air/vapor barrier. R32
-Ceilings were a mix of drop and sloped, we are removing the drop ceilings to reveal the sloped 2×6 rafters and insulating with R21 batt. We’re adding 4″ of polyiso to the deck so the total roof r value will be around R45
-Floor joists are 2×10 16″ o.c. , basement ceiling height is only 7’8″ (once I remove the furnace plenums). The goal of this project is to maintain ceiling slopes and heights. Unfortunately it doesn’t leave room for new duct work.
-Approx 350sq ft of the home is a sunroom that we are converting to living space. It’s got nearly 450sq/ft of glass probably a heat load of 12,000btu/h.
Because the ceilings and walls will be open (and the water heater needs replaced) it’s a good candidate a hydronic retrofit. I understand the heat load is important. I believe it will be around 35,000 btu/h. By the time this gets ordered/installed we’ll have a heat loss calc. It’s critical that the system is as simple as possible. From the get go I assumed wall radiators with TRVs, home run, and a HTP phoenix light duty water heater (for those unaware it’s a modulating, condensing, tank water heater with internal heat exhanger). I like that it’s mechanical, zoned, and straightforward. The phoenix water heater and TRVs appear to drastically simplify the system. I’m now considering using radiant walls or ceilings so that the heating is concealed. The sunroom conversion will be built over slab so we could go radiant in that floor to help cover the load.
Fabbing the wall or ceiling panels is straightfoward to me, but I am confused on the ability to maintain control of the panels with a TRV. Searches along heating help and others suggest the loop length needs to be kept down and suggestions for an Oventrop unibox. Can someone help me understand how a TRV would install in this application?
What do you do around electrical outlets with the heat transfer plates on radiant walls? Is there a clearance requirement? For example, if the outlets required 1′ clearance on all sides I may go with the ceiling for the easier install.
Long story short. I think hydronic heat retrofit is the best fit all things considered on this project. I’m prepared to go HTP Phoenix with radiators on TRVs. I’m willing to put the extra work into concealing the system into ceilings or walls, if I can maintain control with the TRV. Any thoughts?
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