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How to heat an attic in an old house with radiators

I own a 1920 house and want to turn a walk-up unfinished attic into a playroom for my kids. The problem is that we have hot water radiator heat in the house and I'm not sure how to heat the attic. How hard would it be to add a radiator on the third floor? Or would you recommend a different form of heat? And if so, what would you recommend?

Re: How to heat an attic in an old house with radiators

Perhaps the easiest way to approach this would be to verify that you have sufficient extra heating capacity with your current boiler, and simply extend the hot water heating system using PEX piping and hot water baseboard.

There is usually enough extra capacity on the boiler, but a heat loss calc would have to be done to determine the square footage of the attic, presence of insulation, etc.; cast iron radiators can be used, but they weigh hundreds of pounds, are bulky & have other disadvantages when compared to standard aluminum-fin baseboard.

Best bet is to consult the Yellow Pages under "Heating Contractors" and have several jobbers come to the house to give you a written estimate and price estimate for the job.


How about 2 birds in one stone? You could do a mini-split that could provide both heating and cooling. Would be efficient and a cost effective way without having to distrupt your existing heating system.


Re: How to heat an attic in an old house with radiators

Thanks for the advice. I will look into both. Forgot to mention, though, that the existing furnace is from 1920 also, so not sure we can add to it.

Re: How to heat an attic in an old house with radiators

Oh,no! ------there is NO way you should allow yourself to continue using a boiler that old in this day and age!

A 90-year old boiler is from the stone age by today's standards; most of them of that vintage actually began as coal-fired units that were then converted to oil or gas-fired boilers---they tend to be very inefficient, where often 50% of the heat produced is going right up the chimney to heat the great outdoors.

Given the cost of today's heating fuels, you are losing serious money each winter that you allow a fuel hog like this to continue to sit in your cellar.

Replacing your present boiler with even an entry-level cast iron low-cost replacement will give you a boiler that returns 83% or better fuel efficiency.

You have to realize that there have been tremendous improvements in the design of boiler combustion chambers and other components in recent decades by European and American heating engineers that make a new boiler burn fuel in a much more economical way.

If you are using oil, that means a drop of close to 50% in your fuel usage; a natural gas unit would see similar savings--with the fuel savings you see in a few winters, you will recoup your investment completely.

Also have someone check the insulation in the exterior walls of your house, and have cellulose insulation blown in, if needed; storm windows or double-pane modern windows are also a necessity; these measures will pay for themselves within 2 heating seasons!

Re: How to heat an attic in an old house with radiators


I understand your point, but since we bought this house in 2007 and it's worth about 40% less than we paid for it, it's hard to justify the expense of new furnace, new windows and new insulation. We have storm windows so it's not terribly inefficient and our gas bills aren't terribly high. The furnace is a gravity boiler with hot water heat. I've been told if we start messing with the furnace it could mess with the entire system and, in my book, if it ain't broke, don't fix it. So replacing the furnace isn't really on the list right now.

Re: How to heat an attic in an old house with radiators


I can see your point.

I had no idea that you had a gravity HW system, which is quite unusual in this day & age.

I agree you should perhaps stand pat until circumstances improve.

Re: How to heat an attic in an old house with radiators


Can you even replace a gravity HW furnace today? Does anyone make them? Or would it require changing the entire system? And what does that entail? We like the heat from the radiators since it's not so dry. Can they be converted to steam or is there a new approach to HW with a new furnace? Thanks!

Re: How to heat an attic in an old house with radiators

I think it's well worth the effort to have several heating techs come over the house & give you a written estimate for putting a new boiler in along with the 3/4" plastic PEX tubing to connect all the rads & just leave the old piping in place.

I would recommend keeping the rads in place, as they are an excellent source of heat & are much better than baseboard.

Steam heat is rarely installed in homes these days (requires daily maintenance) & you would probably not be able to use the current rads if you opted for steam.

This would involve a new boiler from say, $2k to $4K for a unit that's 85% efficient or better; the rest of the cost would be the labor to install 3/4" PEX plastic tubing thru the walls to every rad & leave the old copper lines in place; there would be various other fittings such as a circulator pump, zone valves, air eliminators, etc.

The total cost may be in the vicinity of $8k--- but who knows---it could be lots more---that's why you should get at least 3 estimates.

You would then have to determine if you would be able to pay off this amount over the next few ensuing years via the fuel savings you would realize from the more efficient system---in other words, how many years of fuel savings would it take to get a return on your investment---if it would take 10 years or more, & you're not sure you will be living there that long, it may not be worth the expense.

It's common for new refits to see a 40% drop in annual fuel usage---particularly with the system you describe, that has a very inefficient boiler & has to heat up a lot of extra water in those very wide distribution pipes---you may have 50-70 or more gallons of water in your system now, where a PEX distribution system would have 15 or 20.

The difference is an efficient boiler, & a small energy-efficient circulator pump that can quickly get the hot water to every rad in the house.

In your case, I think you will see such a dramatic drop in fuel usage---the PEX system would have much less water to heat to supply to the rads, & the higher efficiency of the new boiler would also add to your savings.

How much do you pay now annually for fuel?? What is the total square footage of the building?? Does it have insulation in the exterior walls??

If the exterior walls need insulation, a few hundred $$$ would be all it would cost, & would save a lot on fuel; there is now a rebate on your federal income tax if you put in new windows, but the storms are probably ok.

Please post your annual fuel expense & the other info requested.

Gravity to Hot Water

Yes you could convert it as Nashua has said. Although you don't need 3/4" pex to the rads.

You would install a radiant manifold using 1/2" pex and possibly 3/8" depending on gpm requirement which would be dictated by the heat loss. You would also want thermostatic radiators valves on the rads. This gives you the ability to control each room individually. You could keep unoccupied rooms cooler the occupied rooms. Would also use a circulator pump that maintains designed delta-t such as a Taco VDT as a system pump. Boiler would have outdoor reset on it be at a minimum 86-87% efficient if oil.

I would atleast take a look at converting from oil to LP and compare the cost of installing a gas condensing boiler. Condensing boilers play real well with radiators but also cost more then tradiational pin-style or 3-pass oil boilers.

As Nashua has suggested get a few contractor opinions. Make sure they do a heat loss of the home and measure the radiators to calculate capable btu output.

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