Home>Discussions>INSULATION & HVAC>Best way to manage hot water radiator heat?
4 posts / 0 new
Last post
Best way to manage hot water radiator heat?

Hi, I'm new here, but I've already gained quite a bit of valuable information.

My wife and I just purchased our first home, and it has an oil furnace (approx. 2011 model) with hot water radiators in each room of the house. The bill of sale says the house was built in 1940, but someone else told me it looks more like 1840. I've lived in old houses before, but not one with hot water radiators. We will be replacing the windows, but I'm still concerned that the system might use a lot of oil in the cold winter months. Does anyone have experience with TRVs (Thermostatic Radiator Valves) to control the temperature in each room, or is one thermostat sufficient? I know you can adjust the valve on each radiator, but is that good enough?

I've also been looking at radiator covers which can divert the hot air into the room, and possibly save energy for other rooms.

Each of our radiators has 2 pipes coming to it. Does the hot water run through each radiator before going to the next one?

Re: Best way to manage hot water radiator heat?

Do you have natural gas in your home? do you use NG for cooking?

If you do, maybe it's time to salvage the oil burning system and move to natural gas boiler. Maybe you can get lucky and have a tax credit or a rebate to help you with the capital investment (do the research). Oil is so last century and expensive too. Not to mention possible leaks in the oil tank - waste of money and harmful to the soil.

I have a friend who had an oil burner. His oil supplier sold him a full tank in the spring, showed up at the fall, measured the oil level and told him he needed half a tank...my friend never used the heater during the summer. Half a tank leaked out. Needless to say, I suggested he converted to NG, which he did the following week.

The NG system installer does one a day, 5 a week, that's all he does - converting oil to NG. He has a sub to remove the oil, the tank or fill the tank with concrete slush. He has a 30 day back log, what a business.

Re: Best way to manage hot water radiator heat?


Please provide the info asked for in regards to your general location, whether you have underground gas line service in your area, & also if you can determine (by calling the local oil delivery co., or the previous owner) how many gallons of oil the heating system burned this past winter---the important thing is not to panic or get discouraged; regardless of how high the heating costs were the past winter, THERE ARE a lot of things you can do for a relatively small amount of $$$ expenditure to get your house envelope more efficient so that you will cut your heating bill expenditures IN HALF by the time the winter rolls around.

Your initial steps should be exactly what you've been doing---1) installing new windows; 2) examining exterior wall & attic insulation; 3) getting an exact figure for last year's oil usage; 4) calling your local gas co. or local public utilities commission to determine if you have a buried gas line service along your street; 5) learning as much as you can about hot water (hydronic) heating systems, boilers (you have a boiler there, not a furnace), insulation, radiators, & relatively minor modifications to your present heating equipment you can do that can substantially reduce next winter's heating bills.

Regardless of the bad rap that oil heat has been getting in recent years (the New England area has historically been the only area in the U.S. that still extensively uses #2 fuel oil) the reality of the situation is that there remains very wide areas across the U.S. where home heating natural gas via underground pipelines is NOT available---usually because the local gas co. in each area has to foot the very expensive often prohibitive cost to install underground gas lines in most, or NEARLY EVERY STREET in a given community--despite the reality that nearly ALL natural gas supplies are of U.S. origin (unlike Arab oil) & that there is presently an overabundance of natural gas supplies (driving the price way down) due to improved extraction methods (fracking)---many local gas companies will wait until a given town has to dig up its streets to replace outdated municipal water supply or sewer piping & will then contact local homeowners in the area & offer gas service for a shared fee.

So for those homeowners living in cold areas who don't have the natural gas option & need winter heat, they are forced to choose fuel oil, liquid propane, firewood, wood pellets, electric heating, geothermal, solar, etc.

After you change out your windows, your next step should be to have someone check the amount (if any) of insulation in your home's exterior walls (R19 required) and attic (R40 required); consult the Yellow Pages under Infrared Inspection Services, or under Insulation to have a contractor do a heat loss test to see where most of the heat loss of the building is occurring; you can visually check the attic---you should have at least 1 ft. of insulation there; usually you can check the exterior wall cavities via the attic or cellar to determine if there is any insulation there; if not, it is money well-spent to have cellulose insulation blown in---this strategy is to visualize the house as an INSULATED ENVELOPE---if there is no insulated envelope (which includes new double-pane windows), it doesn't matter how much heat you produce or oil you burn with your boiler---it will quickly escape the house & the boiler will keep firing wasting oil & $$$$.

Adding more insulation pays an ADDITIONAL DIVIDEND for the summer months when the house needs to be kept cool to be comfortable---in summer months the insulation acts as a barrier to prevent hot summer air & humidity from entering the home & greatly reduces the cost of running air conditioning---that's why insulation installation is such a wise investment.

Before next heating season starts, have someone check out the boiler; if you have a recent vintage boiler from 2011 it will be much more fuel-efficient to begin with (unlike most other types of heating equipment, oil burner fuel systems can be substantially modified to reduce fuel usage); look at the faceplate of the unit & let us know the input capacity, as well as the output capacity (both in BTUs/hour); the output should roughly match the total square footage of the house multiplied by 35 BTU/square ft. (assuming 8' ceilings & accounting for your geographical location); if you have a service call in the near future to annually clean the boiler, ask the tech the rating of the fuel nozzle (in gallons per hour) & if it's oversized considering the square footage of the house; it is often feasible to "downrate" or reduce the fuel nozzle (install a smaller nozzle) from over 1 gallon per hour oil use to less than that figure---this will save a lot of fuel oil for the winter heating season.

The radiators---do NOT make the mistake of condemning the cast iron radiators---it turns out that cast iron radiators are like a precious metal--they are the best part of the system--they are often given a bad rap for being "old fashioned" & clunky; but this is from people who don't understand the superiority of forced hot water (hydronic) heating over forced hot air, or most other forms of residential heating---when the rest of the heating system is working right, the rads (convectors) will absorb a lot of the heat from the hot water & continue to emit it for hours after the boiler has shut down (saving fuel); no other convector has this quality; a forced-hot water heating system, btw, is considered top of the class in residential heating, not only in the U.S., but around the world.

You note in your post that your rads have individual shut-off valves---this would indicate that you can control the heat going to each rad by experimenting with the on/off position of the valves---if one room is too hot, by all means turn down the control on that rad---this will allow another room that may need more heat to warm up more rapidly.

Thermostatic Radiator Valves (TRVs): TRVs and Zone Valves are ways of controlling the heat of individual radiators (rads) usually in a particular room or area of the house that presently feels less than comfortable---I would concentrate on the other areas mentioned in this post before dealing with TRVs or Zone Valves---as you note, you have knobs on the rads that can control the heat going to each rad, so the expense of using TRVs in your case would seem to be redundant; sometimes in LARGE HOMES (say, with 2 floors or large rooms) the 2 floors can be zoned off with zone valves, where a T-stat would be installed on each floor for better separate heat control of each floor; the site following has diagrams at Figure 5-13 illustrating how TRVs are piped to each rad & usually have to be set up with supply & return MANIFOLDS---this gets expensive, & as noted, probably isn't needed in YOUR case; you can Google "thermostatic radiator valve diagrams" to get additional sites as to how TRVs are piped.


Briefly, how a hot water system works: the thermostat on the living room wall closes initiating by wire a 24 volt "call for heat" to the boiler when the living room/house gets cold--the oil burner converts the 24V signal from the t-stat to 120V to fire the oil burner motor/fuel pump; the 120v is converted briefly to a 30,000V ignition spark to ignite the fuel oil spray in the boiler combustion chamber; once the water temp inside the boiler water jacket gets to 160 degrees, 120V is supplied to the boiler circulating pump to circulate the hot water thru the BOILER MAIN SUPPLY PIPE to send the HW to each of the radiators in sequence; the cooler water sitting in the rads throughout the house is forced back into the boiler via the MAIN RETURN PIPE to be heated; this heating cycle process is continued until the T-stat in the living room is "satisfied" & the increased temperature in the living room OPENS the contacts of the T-stat, closing down the boiler; the circulator pump will continue to circulate the HW thru the rads until the water temp drops to 140 degrees & the system shuts down until the next call for heat.

To learn more: it's easiest to start at the local library; ask the librarian for books on residential hot water (hydronic) heating & concentrate on those books that have lots of diagrams of HW heating systems, boilers, pumps, zone valves, TRVs, etc.

Re: Best way to manage hot water radiator heat?

Yo, how high are the ceilings in the house????

If you have ceilings that are 12 ft. high or higher you might want to think about dropping them to 8' with sheetrock/acoustic tile to save on the heat & ac.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.