Heating Improvement Options.
We have an old (1939) 2 story brick colonial. Heating costs and comfort have always been a problem. We are looking for heating efficiency improvement options.
We have a one zone forced hot water (gas) system that feeds rectangular flat cast iron radiators. We set the thermostat at 68 degrees that barely keeps the first floor comfortable and the second floor chilly (61-63 degrees). We have installed double pane replacement windows (CertainTeed) but the house still feels drafty. We have to install plastic insulation sheets to help.
Are there suggestions / recommendations for options. Would adding a separate zone for the second floor be a option? We thought about using a gas stove fireplace insert. Would this be an efficient alternative? Can this produce enough BTU's and warm the house more evenly? Is it a cost efficient alternative?
We are scheduled for an energy efficiency audit from National Grid. We are open to their suggestions / recommendations with regard to improved insulation and upgrading to a higher efficiency furnace.
Any help from the TOH community is appreciated!
Last edited by our old house; 02-21-2009 at 01:51 PM.
Re: Heating Improvement Options.
Our Old House:
I'm glad to hear you're having an energy audit done----but don't let them sell you any heating equipment, at least in the short term before you pinpoint exactly what you must do to tighten up the house & check out the heating system to make sure it's putting out sufficient heat for the building's needs---you mention "drafty" conditions, so something needs a lot of work---more insulation, more window caulking, more heat output from the rads, more rads, whatever---if you're still getting drafts from the windows even after putting up plastic sheeting, the windows are still a problem---they may have been improperly installed.
Heating brick buildings can be a problem due to the often difficult task of trying to get any insulation in between the walls---if there is no space between the exterior & interior walls, conventional blown-in insulation is not possible.
Is the heating system itself putting out sufficient heat???---try touching the incoming piping to the radiators (just for a second or two) when the heating system is running---the pipes should be hot enough that you can't keep your finger on it for more than a second or two---if the pipes are at their proper temperature (180 degrees), you'll pull your finger away very quickly---you can verify the boiler temperature by going to the boiler room and checking that the boiler gauge reads in the 160-180 degree range while the system is heating the building.
Are all the radiators hot to the touch when the system is heating up???---as with the finger test, you should not be able to keep your hand on any of the rads for more than a second or so while they're heating up (be careful & don't burn yourself)----if all the rads are hot enough to pass muster, do some calculations to determine if you have sufficient radiator heat output to heat the building---if any of the rads are only lukewarm, post back for techniques to get them heating at full throttle.
To get a rough heat output of a particular room (assuming 8' ceilings), take the square footage of the room and mulitply by a heat factor of 40 to get a rough heat loss of the room per hour.
Thus, a room 15 X 10 = 150 sq.ft. X 40 = 6000 btu/hour---this is roughly the amount of heat being lost from the room to the outdoors per hour on a cold day, that must be made up by the rads to keep the room warm---next, measure the heat output of the rad(s) in the room---this is done by assigning 170 btu/hr for each sq.ft. of rad, then multiplying by the # of rad sections.
Thus, a 24 section rad which is 1/2' wide and 1.5' high = .5 X 1.5 = .75 sq.ft. X 24 = 18 sq.ft. X 170 = 3060 btu/hr output of this rad (at 180 degrees water temp).(there is a thin vertical line between each rad section that separates it from the others & constitutes an individual section).(the outputs stated are calculated for when the water temp is 180 degrees---if it is less than this, the output will be lower).
In this example, there would have to be at least 2 rads of this size in the room to provide adequate heat to keep the room warm: 3060 X 2 = 6120 btu/hr---the rads work best if they are directly under a window.
The entire heated space of the house can be calculated from the above formulas---if the total sq.footage of the house is, say 1500 sq.ft.: 1500 X 40 (heat factor) = 60,000 btu/hr is roughly the total heat load needed in btu/hr for the house---read the boiler i.d. tag--it should say something like "output: 60,000 btu/hr. somewhere on the nameplate of the boiler---the heat load of the house should roughly jibe with the heat output of the boiler to verify that the boiler is big enough to heat the house.
Please post back with any info you gather, on the age of the boiler, your general location, & especially on if there is a space between the bricks where some insulation can be blown in.
Last edited by NashuaTech; 02-21-2009 at 02:36 PM.
Re: Heating Improvement Options.
Thanks for all that information! I performed the touch test as suggested. Surprisingly there isn't a radiator in the house that has that too hot to the touch feeling. The furnace gauge while circulating was showing about 135 degrees at @25 psi. What were those techniques to get them to heat at full throttle? Does this require significantly more energy use?
Other info you were asking for: we are in Central MA., the furnace is a Burnham low pressure boiler, 1977. The tag shows a DOE Htg. Cap. - 139,000 Btu / hr.
I measured the rooms and sized up the radiators. I can finish the calculations after trying the full throttle method.
With the insulation, I'm not sure how accessible the exterior is for blown in insulation. The interior walls are a plaster and wire lathe combo.
Appreciate the help!
Re: Heating Improvement Options.
Cast iron radiators are designed to operate at 180 degrees in order to effectively heat a building.
If your rads feel only moderately warm to the touch, and the boiler gauge doesn't go any higher than 135 degrees, even near the end of the heating cycle, then the HIGH LIMIT inside the aquastat has to be set to 180 degrees---there is also a LOW LIMIT in the aquastat that should always be set to 20 degrees cooler than the HIGH LIMIT, or 160 degrees for the LOW LIMIT.
A photo of a typical aquastat is pictured at the site below-----one or two small screws have to be removed from side of the steel cover to pull off the cover to access the circular knobs that are also pictured in the site below.
First, shut off the boiler on/off switch, then remove the aquastat cover & adjust the two knobs, as noted.
It should be noted that you will not typically see the temp needle gauge on the boiler register 180 degrees right away---during the first stages of the heating cycle, the boiler has to heat the water in the boiler itself to at least 160 degrees, then the circulator comes on to pump the heated water to the rads, but the rads are full of cold water, so it may take 20 minutes or even more before all the water in the system gets to 180---you can start a heating "cycle" by simply turning up the room t-stat, then going down to the boiler to watch the action.
If not done recently, go around to each rad with a screwdriver & small cup to bleed the radiators from the bleed valves to get all air out so they will heat more efficiently.
The rooms should feel much more comfortable in less time than before---once the water in the system reaches 180, the BURNER will shut off, but the CIRCULATOR will keep on pumping the water thru the system until the room temp where the t-stat is located is satisfied & the system shuts down---the rads will stay hot for an hour or two after cycle shutdown until the t-stat again calls for heat---if you find that this burns considerably more fuel in the coming weeks, you can always adjust the aquastat to 170 hi and 150 lo later on.
Your psi, as noted on the boiler gauge seems slightly high---if you have an old style expansion tank, it may be slightly waterlogged---if the psi reaches 30 on the gauge, the PRESSURE RELIEF VALVE will automatically open (especially near the end of the heating cycle) & drop a quart or so of water on the boiler room floor---no big deal---simply put a gallon bucket under the overflow tube to catch any water that may come out.
Burnham makes good boilers & the one you have should last for years, but it's old, as boilers go---boilers of that vintage rely on hot flue gases of 600 deg. to blow the combustion byproducts up the chimney---thus they are rarely more than 70% efficient, & may be down to 60% efficiency now---I would still estimate the boiler output at approx. 90,000 btu.hr.---you can have a combustion analysis done ($50) to determine current efficiency.
On insulation, if you have spacing between walls, only one brick here & there need be removed to blow in insulation---strongly recommend you get an estimate for this, as well as any insulation you need for the attic to get it to R40---insulation costs $400 or so, which is a low-cost way to improve your heating efficiency---and cooling in the summer.
Last edited by NashuaTech; 02-23-2009 at 03:43 PM.