Solutions for Varying Temperatures Between Floors
Hi all,
Last winter, we did a major project in our completely uninsulated attic in a 1910-era duplex, climate 4a. It was 2 inches of closed cell foam on the inside of the roof and gable walls and then we spent soooo many hours installing R-23 mineral wool batts in the non-standard width rafter bays (and furring out those rafters with polyiso strips) and drywalling the gables. (Chose to insulate at roof rather than floor because there are stairs to the attic and because there were only 9 inches of space in the floorboards).
Pictures here
We were hoping after thousands of dollars of investment, this would solve the problem of it being distinctly colder upstairs than downstairs.
Unfortunately, no.
I’m going to share with you maybe an eye-glazing amount of data below, but the reason I’m doing so is I want to learn lessons for when we replace our 25ish? year old McLain hot water boiler with a moderating condenser boiler. I would hate for the problem to get worse after we spend $10,000 more. (I would not say it is worse this winter than last, and it may be a little better, as we didn’t track temperature before finishing project, but it’s definitely still a Thing.)
The background — location, Washington, D.C., side by side duplex of about 1,300 sq ft plus unfinished basement and attic.
Built in 1910, stucco, no insulation in walls, but storm windows on all the windows but a few that open on enclosed porches. Most of the storm windows are new upgrades, Larson low-E glass.
We tend to keep the house at 68 degrees most of the time, with a 2 degree swing value on the thermostat. We let it fall to 63 degrees overnight, and then start warming up to 64,65 or 66 degrees at 6 a.m. and then up to 68 degrees by 9 a.m. now that we’re working from home, and stays there all day/evening until 11 p.m.
The thermostat is in the dining room, which has three large windows with East exposure and only one exterior wall. Not sure to what degree the solar gain factor, as I’ve moved the thermometer from our bedroom (north facing, and with two exterior walls) to the middle bedroom (east facing, one wall) and the temperatures are the same. But the tiny back bedroom, which has one east window and an exterior door with some glass to the south-facing enclosed unconditioned porch was 68 degrees at dusk when living room is 68 degrees, north bedroom is 66 degrees, and it’s 38 degrees outside.
(tiny back bedroom is 8.5 feet by 10 feet, has radiator 51 inches by 23 inches, though it is inside a wooden radiator cover with brass preforated front to create more ‘counter’ space in the room, that serves as a home office.)
The dining room has a 58-inch long cast iron radiator, painted silver, 20 inches high. There is also a radiator in the hall at the foot of the stairs/just inside a door that is four feet from the real front door (which itself now opens to an enclosed porch). That hall radiator is 34 inches high and 38 inches long. It’s painted white.
The master bedroom has a painted silver radiator that’s 51 inches long and 23 inches high, painted silver.
All the rooms besides tiny bedroom are about 12 by 12, give or take a foot.
So.
after many days of tracking, the pattern seems to be
the dining room either reaches the set temp or overshoots by a degree
the bedroom can reach the set temperature when the boiler is running (especially when it’s running for more than an hour straight to heat up from 63 overnight) but as soon as it stops running, it quickly falls by a couple of degrees.
This doesn’t seem to be affected by how cold it is out.
So for instance, it’s 57 degrees outside.
When the boiler is running, it’s 69 degrees on 1st floor, 68 upstairs, and 61 degrees in attic.
Boiler stops for a good while, it’s 67 degrees on 1st floor, 64 degrees upstairs and 61 in attic.
It’s 30 degrees outside, and the overnight setback was 61 degrees, with starting to warm to 66 at 6 a.m.
It fell to 59 degrees in the bedroom (and 55 degrees in the attic) overnight, but by 7:30 a.m., it’s 64 in bedroom, 66 downstairs and 55 degrees in the attic.
Then at 11:30 that day, 69/66/55
Then at 2, or it’s 53 degrees outside
67/64/57
We did an experiment, turned up the thermostat from 68 to 70,
and it went from 66 to 68 in the bedroom, when the attic was at 59, but when the boiler cut off, it fell to 66 again while the dining room was still at 70.
I put shrink wrap plastic over the attic windows. We installed a new proper steel slab door with insulating core in the basement to replace an indoor-quality wood door, and one new window. Haven’t yet foamed a small hole I found near old window frame in cinderblock basement wall or shrink wrapped remaining window, but the attic shrink wrap didn’t make any change in attic temperature or second floor temperature. Generally, attic ranges between 54 and 59, but mostly 55-57. Basement is 59 degrees when boiler not running right now, outdoors temp is 38 degrees. It tends to warm up by 2 degrees when boiler is running.
Whew. If you’ve gotten through all this, you’re AMAZING.
Seems our solutions are fairly limited. We can’t insulate basement because it’s not dry (it does have fiberglass insulation in ceiling, installed with the kraft paper the wrong way by previous owners. Don’t know if that’s doing anything good or is actively harmful).
We might be able to add insulation on the top of the roof when we reroof, but from the looks of this forum, it’s hard to find someone in D.C. who knows how to do that (and I wonder if it would make a difference, given this doesn’t seem to have made as much as we’d hoped).
The way the stucco is applied makes insulating the walls not a great idea.
Would stripping the paint off the radiators be necessary to get comfort wtih condensing boiler (I believe those run at a cooler hot water temperature)? Or is that only necessary in the ‘problem’ rooms? Is the radiator cover a definite no-no with the new boiler?
Would it be advisable/possible to install a larger cast iron radiator in the front bedroom, given the pipes go through the floor at a certain width, and the radiator comes up 2 inches below the window sill?
Is there some kind of radiator check up we should do? (We had a boiler check up and learned that it needs to be replaced, but were waiting to get a season of natural gas usage post insulation to figure out what size new boiler we need. Do not know the BTUs of current Weil-McLean boiler)
We don’t mind sleeping in a cooler room (in fact, we prefer it somewhat cooler to sleep in the winter), so perhaps we should just live with this? If we get foster kids (we have been licensed), we’re required to keep thermostat at 70 anyway…
Mara aka 1910duplex
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Replies
Your problem is that your upstairs loses heat more quickly than the downstairs, and they're both controlled by the same thermostat, which is downstairs.
There are two solutions. Either improve your insulation level so that both floors lose heat at the same rate, or break your heating system into two zones with a thermostat on each floor.
In old houses, usually the lowest hanging fruit for improving insulation is air sealing. An airtight house will generally have more even heat distribution.
How difficult it will be to break your system into zones depends on how it's plumbed. It could be simple, or it could require ripping up the house.
I don't know if it was the case in your house, but sometimes adding insulation makes heat distribution problems worse. With the added insulation the heating system runs less overall, which means parts of the house which were underheated before get even less heat.
HOw is your system plumbed? There are a couple variations on how the radiators are run
this is why I ask:
When you have rooms that never reach thermostat temp, the answer is to make the hotter rooms harder to heat. IF your radiators are plumbed such that they can individually be throttled down, like in a diverter T system, turn down the radiators that are closer to the thermostat and are warmer. This will make the circulator run longer and pump more heat into the colder rooms before shutting off.
Do obviously check for air leaks in the colder rooms. It takes a small amount of air leakage to make a room run cooler
Do the radiators have knobs where the pipe enters? Those are "balancing" valves. The idea is you can reduce the heat output of an individual radiator by slowing the flow of water through it. There used to be a lot written about balancing radiators, the idea was you start in the coldest room of the house and turn that radiator on all the way. Then you go to the other rooms and turn them down until the temperature is reasonable. The idea has gone out of fashion because it was time-consuming and never worked that well, the heat load of a house varies too much based on conditions and the knobs don't offer that fine of a control. But it may give an improvement.
If your piping is such that zoning isn't practical, you might want to look at auto-balancing systems. You can get thermostatic balancing valves that shut off the radiator in a room once a certain temperature is reached. An example is here:
https://www.supplyhouse.com/Danfoss-013G8019-3-4-Angle-Thermostatic-Radiator-Valve?gclid=CjwKCAiAwrf-BRA9EiwAUWwKXjzyabhL-19RbwMJlbcoXC_I3ib2EZWjoMKr34MyWAqmLcfkaYE9OhoC_lUQAvD_BwE
They're only about $35 each, which is reasonable if you can install them yourself. It will get pricy if you have to pay someone to install them.
A 1910 house in DC, I'm going to guess it was originally plumbed with a gravity circulation system. In the basement there would be two 2" iron pipes running the length of the house. Each radiator has a pipe running up from each of those pipes. This would be hard to convert to a zoned system.
I would suggest visiting heatinghelp.com and ask questions on 'the wall' before making boiler decisions.
There are strategies for high mass radiators and mod con boilers
and think mini splits.......I have a 10 year old condensing boiler and if the ducted mini splits had been what they are today, I would have saved myself 10k easy
I really think he's going in the wrong direction looking at the heating system. The heating system won't "naturally" make the house evenly heated. It can be working as designed and give the performance he's describing.
Yes, do this. Ask about using thermostatic radiator valves.
Hey all,
I do have knobs on all the radiators. Have no idea if they're able to be turned, what with the painting and all, but it's worth a try!
And yes, there are iron pipes running across the basement.
With regard to the valves, so the idea would be to set the main thermostat to 70, and have a thermostatic valve in every room so that if that room hit 68, its radiator would cut off? How would the boiler ever stop running if the thermostat is set at 70 but no room ever gets to 70?
I'm not really looking at the heating system as a solution for comfort, exactly -- it's more that I have been told I should replace my boiler soon, I want to do so with a more environmentally friendly boiler, but my ability to add insuluation/tighten up is really limited, given the nature of the stucco/plaster wall assembly, and I want to make sure that going to a lower-temperature water boiler doesn't make the situation worse.
What about stripping the paint from the radiators, does that make much of a difference?
Mara
with the thermostatic valves you have to have at least one radiator in the house that doesn't have a thermostatic valve. Normally that would be the one closest to the thermostat. Ideally this should also be the coldest room in the house.
It's hard to say if going to a lower water temperature will make the situation worse or better. From your description it sounds like the upstairs has more radiator capacity but a greater heating load, so when the boiler is on the upstairs heats up more than the downstairs but when it's off it cools off more. With a lower water temperature the heat will be on more of the time which would tend to make the upstairs warmer.
The big concern with going to a lower water temperature is whether your radiators have enough radiation to heat the place on the coldest nights at the lower temperature. The sizing rule is that heat output is directly proportional to the difference in temperature between the radiator and the room. Boilers of your vintage were usually set to provide water with a outgoing temperature of 180F and a return temperature of 160F, which gives an average temperature of 170F. If your room is at 70F that's 100 degrees of difference. If your new boiler is at 130F send and 110F return that's average temperature of 120F and 50 degrees of difference. So the radiator is going to produce half as much heat, which means the system is going to have to run twice as long. If your current system runs more than 50% of the time when it's 20F out (the design temperature for DC) then your radiators aren't big enough to take the water temperature down that much.
My gut says this house is still leaking air like sieve.
Before you disturb the heating system do whatever needs to happen to get a blower door test under 3 air changes per hour.
Walta
Agreed.
Be careful with adjust rad vales that haven't moved in decades. Chances are the stem on them will leak. You can usually tighten up the packing nut (the big nut on the stem) to stop the leak, most of the time this works, sometime you need to replace the packing.
If you do replace your current boiler with a modcon, make sure you set up outdoor reset on it. This will modulate the water temperature based on outside condition and you'll get much longer run times and more even water supply temperature. This will prevent what you are seeing right now when the thermoset shuts off, you can even tweak a reset curve to the point that you don't need a thermostat.
Since outdoor reset will reduce the loop temperature on milder nights, you'll get better seasonal boiler efficiency even if you need to run the rads hot for polar vortex days.
If not cost prohibitive, install TRVs as you can adjust individual room temperatures.
One trick to get lower RWT and better efficiency out of modcons with high temp rads is to run them at much higher delta T (provided the unit can handle it, most can). For example you can supply a rad 170F water but with a 110F return. The rad would put the same heat is if supplied by 150F and 130F return but much better efficiency out the modcon. A delta T circulator can do this adjustment automatically but you can also do it by tweaking the flow rates.
Most likely not the issue, but I had problems with older systems that were converted from gravity feed where the water would not circulate properly. Instead of the flow splitting off to feed the different stories of the house, all the heat would run to one level. You can do a quick check by touching the main return and supply pies in the basement that feed the each level, they should be similar temperature.
+1 on zoning. The need for it is under-realized.
DC Contrarian,
no, the upstairs does not heat up more than the downstairs. Often it doesn't even reach the temperature of the downstairs (except in the South facing tiny bedroom). For instance, right now, the boiler is working on moving from thermostat setting of 65 to 68 (started this process about an hour ago, when dining room had fallen to 64 on 65 set temp). It is 67 in the dining room right now. In the bedroom immediately above, so same window/exterior wall situation (it's a duplex, so the middle room has only one exterior wall, and that's where the thermostat is), it is currently 64. That's the same temperature it was an hour ago, when the boiler came on. Both radiators feel equally hot.
fwiw, it's 36 out now.
[update, boiler just finished, 10 minutes later, when dining room reached 68. It's still 64 in that bedroom]
Walta,
I am sure the house leaks like a sieve. The only place it has any airsealing is in the attic, and it has no insulation in the walls. But I don't think we can improve that, given our constraints. It is not safe to put insulation in the walls, because it is plaster and lathe interior walls and 1910-era stucco over metal mesh, with no air gap. We're not interested in removing the exterior or interior walls, so short of that air sealing mist, I don't know what we could do. We had a blower test done as we were trying to figure out how to insulate the attic last year, but the crappy company didn't give me a proper report, so I never got the ACH number.
Also, DC Contrarian, thanks for the update on the thermostatic valves. I wonder if the best thing to do would be to move the thermostat upstairs??? Wonder how much that would cost.
I will try and pay attention to how much the boiler runs on a very cold day. Definitely on these typical winter days (high of 40 to 45, low 28-33), it runs much less than half the time.
Akos, I will print your advice for when we are ready to get a new boiler! Both the large iron pipes in basement are equally hot right now (boiler just finished) as are the small pipes that run to the second floor that are on either side of the living room and dining room radiator and next to the first floor bathroom radiator.
It's important to note that air sealing is not the same as insulation. In fact, insulation usually doesn't provide an air sealing function. Air sealing is done with caulk in the small cracks and spray foam in the big ones.
I agree it is not worth it to pull down the walls to insulate. But I think you can do a lot with a calking gun, incense stick and a window fan.
In my last house I had a room addition that was very different from the rest of the house it always wanted to be a different temp than the rest of the house. My solution was Honeywell’s most expensive thermostat it had an optional sensor to be placed in that room and the thermostat control was based on an averaged of the 2 sensors. I have not look in years but I think the vision pro 8000 still work that way.
Walta
Tell me more about your technique! I assume you put the fan in the window and then use the incense stick to go around looking for drafts? Do you have the fan blow in or out?
Yes I set the fan to blow out.
The old house had an attic fan that worked well. The new house has a larger range hood that also works.
A bright LED flashlight is also help full.
Walta
I agree with the folks saying that the attention should be focused towards air sealing. 1910 is newer than any house I’ve ever rebuilt. With old houses, in order to get a reasonably well sealed envelope, you basically HAVE to do one of two things.
1. Remove siding and air seal from the exterior.
2. Remove plaster and lathe and air seal from the interior.
Ideally both if you’re focused on efficiency, but one or the other is necessary. Otherwise you’ll be insulating in vain until the day you die (or sell the home out of frustration).
well, *that's* dark! We are going to try tinkering around the edges with radiator settings rather than tearing out walls (though we may also try draft snakes where some windows aren't as tight as they should be). And it's not imperative we get the two moderate size bedrooms to the same warmth as the first floor. The back bedroom, which is the only one used during the day, does get to the same warmth, due to the small size of the room compared to the radiator & the Southern sun.
Can you do a manual J calc for the upstairs (and whole house) and compare that predicted heat load with how much each radiator should be emitting? Maybe it’s just not enough radiator upstairs compared with too much downstairs.
Also compare annual fuel use vs calculations to see if your model is in the ballpark.
One more perhaps interesting piece of data -- we went out of town for a weekend and left the thermostat set at 58. At that minimal level of heating, the cold bedroom was exactly in line with the dining room, where the thermostat is -- the temperature swings over 24 hours stayed between 57 and 59. To me, this seems to suggest it's more a radiator issue than a heat loss issue? Or am I missing something?
There's no distinction between a radiator issue and a heat loss issue.
Here is a simple model of how a heating system works. In a given room, a certain amount of heat flows into that room through the heating system. A certain amount of heat flows out through the exterior walls. The amount of heat that flows out is directly proportional to the difference in temperature between the inside and outside, so a room that loses a certain amount of heat with an interior temperature of 70F and an exterior temperature of 40F will lose twice as much at 10F exterior, or the same amount at 10F exterior, 40F interior. With a given heat input from the heating system and a given exterior temperature, the interior temperature will stabilize at the temperature where the heat flow in equals the heat flow out.
A heating system like yours has a very simple control, it is only on or off. The thermostat is an on-off switch, and it turns the heat flow on and off, based on the interior temperature -- at the location of the thermostat. Ideally, the system is designed so that each room has a heat source proportionate to its heat loss and the interior temperature is consistent throughout the house. But this doesn't automatically happen -- there's no "radiator magic" -- and if a room has a heat loss that is greater than the heat provided, it will be colder than the room with the thermostat, and vice versa if the heat loss is less.
So what's happening is that you've got rooms where the heat loss is not well matched to the heat being provided by the radiator. This isn't a "radiator issue" or a "heat loss issue," it's a mismatch.
Now, the solution is either going to be getting more heat to those rooms, or reducing the heat loss from those room.
When I pulled out 1910 hydronic system apart it was blocked/restricted in various places by scale/rust. It wasn't surprising as nobody would have ever balanced the PH.
Buy a thermal camera to check which parts of the system are working. Some cameras can be used with a Smart Phone.
You can also check the output temp of the boiler and see if the radiators are close to the same (180F??) temp.
When we redid our system we added more radiators so the system could run at 130F which prevents burns. In addition the new boiler has an outside thermostat so it doesn't make 130F water when the outside temp is above 50F
The system was plumed first to last so it is self balancing and we used towel warmers for the open loop.
Or even just an infrared thermometer to see if every radiator is getting hot water.
That all makes sense, DC Contrarian (by the way, we should probably compare notes on contractors, since I am also in DC!). What was interesting to me was that when the delta was not as large, the (usually) colder room and the thermostat room were the same. It's only when I'm trying to heat to a more livable temperature that the radiator in that room can't keep up. (I phrase it that way rather than saying the loss is pronounced, since the room never reaches the same temperature as the dining room when the thermostat is at 68 or 70)
Mara
One thing that would be worth checking out is to confirm that your system is indeed working as designed. There can be simple things like air in the pipes or a failing circulator that won't cause a complete failure but will cause certain radiators to stop producing heat. Those should be eliminated before further exploration.
Our water temperature is not as high as 180, I've forgotten exactly what it is, but I know when we had the plumber/boiler guy come to bleed the radiators, he also turned the water temperature up 10 degrees. (This seemed to help the southern, tiny bedroom get warmer, but had no effect in other two upstairs bedrooms; perhaps made gas bill higher, though.)
The radiators in the colder bedrooms do get warm, and when the boiler is running for a long period to catch up several degrees from night time setback, they do get hot. But I do wonder if there could be a circulating pump issue, given the distance from the boiler is correlated with the colder rooms. The same guy that came to bleed the radiator did a general maintenance call on the boiler two years ago, which showed that if you turn the pilot light down to a normal level, it goes out entirely!
John, I do not understand this sentence: The system was plumed first to last so it is self balancing and we used towel warmers for the open loop.