Is it ok to install vertical hot water radiator in wall recess?

bvz2000

Homeowner here, just starting to plan out a system. I am going to go with (hopefully) an air to water heat pump running to wall mounted radiators in a small home in the San Francisco Bay Area.

I'm trying to find suitable locations for the radiators right now. As I mentioned, it is a very small house (3 bedrooms, but only 1000 sq feet) with very small rooms.

If I opened up an inside wall and lined it with a highly reflective material, could I install a radiator in that cavity? That would buy me about 4 inches of extra space.

Because it is an inside wall, there is no insulation that I need to concern myself with, and if there is any heat loss through the wall, it would simply leak into another interior space that needs heat anyway. I would have to make sure not to hang any pictures on the other side and have nails poking through

But I know that the science of heating is quite complex so there may very well be a ton of reasons not to do this. So I thought I would check here to see if anyone has any thoughts (I will of course also check with my installer once I have one as well...)

EdTheHeaterMan

That would work fine. Back over 100 years ago this was done all the time because it used less pipe. The extra pipe to place them on the outside wall, was something the wealthy folks did.

If you could plan that inside wall to be close to the outside wall that would help a little. here is what I might do for this compact homeOf course there is less heat in the heat pump hot water system. High temperature water might be 130° when it is very cold outside. You need some bigger radiators to heat the same small space as a 180° radiator could do with a compact radiator.

Additionally, by recessing a radiator, you will also cut down on the radiator output. The math is simple but don't forget to include ALL the variables in your calculations. These calculations should start with a manual J load calculation.

To paraphrase a famous credit card commercial. Don't heat a home without it!

Alan (California Radiant) Forbes

I don't think you would need reflective material as radiators heat mostly by convection. More than anything, leave space below and above the radiator to allow for air flow.

And make sure you size the radiators for the low water temperatures from a heat pump; 140° max. They will be large.

These are from a job in Berkeley in 2004.

bvz2000

Oh wow! Thanks so much for such detailed responses!

I am not up to doing the proper heating calculations myself (though I am such a home nerd that I bought and read a book years ago called "Modern Hydronic Heating" just so that I can at least kind of educate myself a bit). But I really appreciate the reminders about the temperature of a heat-pump vs. regular boiler. I figure that when I do wind up working with a heating professional that they will be able to do the calculations for me. That said, it is a good reminder for me to check that they do.

At this point I'm mostly trying to decide between radiators and under-floor heat. Cost is a limiting factor and I am afraid that retrofitting under-floor heat to my home with its super low, uninsulated, full of nails and weird wiring crawlspace might be too expensive - ergo the thought of going with radiators. (Plus I think radiators kind of look cool).

So now I am doing a preliminary look around the house to decide where they may fit. But it would be a very loose set of ideas to be adjusted based on the needs of the heating system.

One more question, if you have any thoughts and don't mind sharing: I have seen something called in-floor heating (I came across something called the Jaga Clima Canal 8 - though I suspect there are many manufacturers of similar products). Would something like that be able to work with an air-water heat pump system? And if so, are they reasonable heat sources (again - S.F. Bay Area so the coldest it ever really gets here is down to the mid 30's, and only rarely at that).

Thanks again so much for the replies (and the detail!). It is greatly appreciated.

gyrfalcon

1 zone of my house has recessed fin tube emitters.  Works fine for this home. Yes, I know I need to clean them!  

bvz2000

Thanks! They seem like a decent way to add radiator heat when you don't have a lot of space.

And as to cleaning... well all I can say is that I am glad that I don't have to post pictures of my wall heater. If I did, child protective services would have to come to my house. And I don't even have children!

Alan (California Radiant) Forbes

That Jaga product looks nice and would be a good alternative for your situation. I've never had good luck with floor convectors, but the 24 volt fan could make the difference and the published BTU output might be able to match your heat load.

Power Boiler Sales in Richmond sells Jaga. I'd call them to see what they think of that particular floor register and ask them for contractor recommendations.

bvz2000

Alan, thanks for the tip. I will give them a call this week.