Help determining most efficient way to heat my second floor

[trachma]

Very long story short: Our old oil furnace died and we are replacing it (After National Grid took our money for a gas line and then refused to dig it before April...don’t get me started. We know gas would be better; we tried; we can’t get through a New England winter without a furnace. Please no lectures on this as we’re still in grief over having to go with oil anyway.)

The whole house is still single zone, and the second floor is significantly colder than the first, which is unlikely to change (unless the ductwork guy is a magician).

I figure we have two options:

A) Turn the house thermostat way down at night and heat the upstairs with electric space heaters when sleeping (cool, but not frigid). 

B) Keep the house thermostat the same as the afternoons (when we’re home) so the upstairs gets whatever heat it gets. Wasteful to heat the whole first floor when no one’s down there, but potentially cheaper than the electricity.

My question is how to test each method and measure for results. The oil tank gauge is very vague — just a floating bob fro which you can guesstimate 1/4-tank increments. My initial thought was to try option A for a week and marking the oil gauge and doing a personal electric meter read at the start and end of the week, then comparing it to the results of the next week on option B. This doesn’t account for outdoor temperature differences, though, and it could get messed up if we have to fill the oil tank or some such nonsense in the middle of the test.

Anyone have a better idea? Hoping for something simple but accurate, and I’m not at all afraid of math! Thanks!

[sokoloff]

Not trying to lecture, but is repairing the existing furnace, even if it means installing an entire new burner unit, cheaper than replacing the whole furnace?

In terms of doing math and figuring efficiency, you might see if the new (or old) furnace can output a "burner engaged" signal, either via an RS-232/422 or some other mechanism (sensing voltage to the burner or hours of "call for heat" from the T-stat). That would be much more effective at gathering relative oil consumption than trying to read the "eighths of a tank" and figure it out. Count hours of runtime, not eighths of a tank.

[Lulee]

I'm in a similar situation with the apartment I rent here in SW New Hampshire --- oil heat in a single zone where the bedrooms in the front of the house are at least 4 degrees colder than the living room where the thermostat is.  When the zero and sub-zero weather hits, it's way colder  than that in the bedrooms.  I have not water radiators instead of forced hot air like you apparently have.  But you have a moist cold there by the ocean which can make things feel worse in my experience.

I tried supplementing the heat with electric heaters.  Works great but is very expensive.  I believe NH has higher electric rates than you do in MA so YMMV.  Mostly I've just learned to live with the colder rooms although if I'm I'll, I'll use the electric heaters as needed.  And my electric mattress pad is my life saver along with my sock monkey hat gifted to me by my SIL as they both make sleeping in a cooler room comfortable.

Agreed that the oil gauge is too vague to use for short term testing purposes.  Could you run the tests for a month at a time, starting right after a delivery?  You'd still need to account for the colder second month impacting things.

Can you get an audit done to see if the system is that unbalanced as to where it sends the heat (perhaps the previous owner liked sleeping in the cold) or if there's some heat loss mitigation to be done to keep what gets to the upstairs to stay inside?

Best of luck and please update us as to how it goes!

[trachma]

LOL – no worries about the lecture! We definitely *wanted* to repair the furnace instead, thinking if we could limp through the year we could get that gas line in the spring. The heat exchanger is broken, though, and the system was spitting soot, ash, and CO into the house, so it’s a goner. The unit is 17 years old, so a (small) silver lining is that we’ll be replacing an 82% eff. furnace with an 86.6% eff. furnace with an ECM.

The reason the furnace tanked in the first place is that the ductwork in the house is remarkably awful — a previous owner’s truly terrible DIY work. That will also be redone, so the heat distribution on the first floor will be much better. But the upstairs will probably not see much improvement, as the ducts up the walls are too small to get the job done — they go up the exterior walls of our 102-year-old balloon frame. We won’t be building a new duct chase any time soon, though because there’s no good place to put it — hence our experiment.

We’ve had an audit and retro insulated the house, but the issue really seems to be the pancaked ducts heading to the second floor (according to everyone who’s looked at the system).

I had thought of drawing our experiment out to more like a month to get a better oil measurement on the tank refill, and that’s probably what I’ll do. I suppose I could go to weather underground and get our average daily temps for each period and do a little math with the average degree difference between the thermostat and the outside to get a better sense of how the environment effects those numbers.

For the more distant future, we were thinking maybe a ducted mini-split in the attic that pipes to the bedrooms on the second floor from above.

Husband and I are totally fine sleeping in a 55-degree bedroom, though getting dressed in the morning is significantly more pleasant at 60 or 62! Our two kids, though, have gotten a taste of those space heaters we brought in while the furnace has been broken, and it might be hard to go back to the cold for them — silly cranky teens who like to hide away in their rooms alone for hours on end! <eyeroll>

[BudgetSlasher]

A few thoughts:

Every multi-story New England oil heating forced hot air house I have lived in has required that the dampers on the ducts (either at the vent or on the duct) be adjusted to balance heating across the house. Basically close the dampers slightly on the shorter runs and leave the longer runs wide open.

You will want to look into a furnace with an ECM motor and hopefully an adjustable fan speed (possibly even with an ultra-ultra low always on speed, or an ultra-ultra low linked to a thermostat that can randomly turn on the fan for part of every hour) to move air about the house.

Also, look into a furnace setup that will draw combustion air from outside rather than using heated interior air for combustion air, which creates lower pressure inside and draws cold outside air in.
Since you are getting a new furnace and want to experiment I suggest either a) getting an oil use meter installed on supply line or b) know the GPH for the nozzle in the furnace and have an hour meter installed (I'm on a boiler so it would be on the burner not the boiler, not sure about a furnace). Those will give you a much more accurate fuel use.

If you are tracking fuel use be sure an account for heating degree days; on a colder day you will burn more oil no matter the setup and January will likely be colder than December.

If you are buying an oil furnace I assume that you are staying on oil . . . or are you going gas sometime quickly? If you are staying on oil I would look into whether your state has converted to ultra-low sulfur heating oil (basically on road diesel) or if you can have it delivered. Most states in the northeast are transitioning over the next few years. If and only if you have ultra-low sulfur heating oil I would look into a condensing fuel oil furnace (I know they make condensing boilers, so I assume they make furnaces); they have efficiencies in the 90's, but high sulfur fuel will create sulfuric acid in the condensation and eat away at parts over time.

[gmp029]

Is propane an option? Then you can get one furnace, and use propane for this winter, and then convert it to natural gas in the spring (Assuming conversion is possible, I think it is). Also any leftover propane can be used for your grill.

[Spork]

Is propane an option? Then you can get one furnace, and use propane for this winter, and then convert it to natural gas in the spring (Assuming conversion is possible, I think it is). Also any leftover propane can be used for your grill.

This seems like a reasonable idea.

Usually conversion is as simple as swapping out the orifices (or adjusting them if they are adjustable orifices.)  And lots of propane companies will rent you a tank.  I'd always thought renting a tank was lunacy, but in this case it seems like a good option.

Down side: Propane is expensive.  Down south, we use it and don't think much about it.  I had an acquaintance up north that was complaining of thousands of dollars per month for propane use.  I don't know him well enough to know how excessive his use is or how large his house is, but he was spending more per month than I'd spend in a year.

[trachma]

We also considered propane for this winter and then converting the furnace to natural gas when they could dig in the spring. When they came out for the site visit, the propane guys told us our property is, apparently, wildly unsuitable for an above-ground tank with the setbacks, slope of the front yard, and our landscaping. We have a rather enormous garden with some serious hardscaping that we’re not willing to demo — you can see it from space!



So the most efficient oil furnace we could get is an 86.6% ECM with three fan speeds. All new ductwork in the basement to reach the first floor and improve return air is coming as well. This is a done deal (or will be once it’s installed next week).

For the second floor, the ducts in the walls reduce the airflow by at least half because they aren’t sized properly. I expect the duct magician to do his very best to even things out, and I’ll keep in mind playing with the dampers as well if it’s still cold.

[dess1313]

Am i wrong or are there not booster fans you can get installed in ducts for long runs to help move air better?

You could also look at some small oil filled radiators set on a timer for the bedrooms.  They're safer than space heaters, and can add a lot of warmth.  timers would allow you to have it warm up for 3 or 4 hours when you're getting up, or when the kids are home in their rooms in the evening

Good luck, you get some nasty winters like we do

[trachma]

Am i wrong or are there not booster fans you can get installed in ducts for long runs to help move air better?

You could also look at some small oil filled radiators set on a timer for the bedrooms.  They're safer than space heaters, and can add a lot of warmth.  timers would allow you to have it warm up for 3 or 4 hours when you're getting up, or when the kids are home in their rooms in the evening

Good luck, you get some nasty winters like we do

I’ll definitely ask Mr. Ductwork about the booster fans on Monday when he gets here — that sounds like perhaps the best solution for our problem.

We have an oil filled radiator in our bedroom we’re borrowing from a friend and I really like it! We’re doing our test with a smattering of on-loan space heater, and I think I’d go with those radiators if we end up going that route.

[Lulee]

Sounds like you've got lots of good ideas and good help to work out a new plan for the second floor heating.  Dropping new ducts in from the attic seems a real wise consideration.

I wish I had remembered this earlier.  Ask This Old House had an episode with Rich Trethewey meeting up with an inventor who had a way to use software and automated dampers in the floor vents to allow each room to be its own heating zone.  Found a link to their site --- https://www.ecoventsystems.com.  I wouldn't have been as impressed if Rich hadn't been so excited about it.  I tend to be sceptical of software based solutions for such physical issues but Rich, after upgrading a house with the Ecovents inventor and talking with him about concerns, was even more enthused than he had been at the start.

As an aside, what an extraordinarily beautiful garden you have, even from above!  Well worth preserving.

[trachma]

Sounds like you've got lots of good ideas and good help to work out a new plan for the second floor heating.  Dropping new ducts in from the attic seems a real wise consideration.

I wish I had remembered this earlier.  Ask This Old House had an episode with Rich Trethewey meeting up with an inventor who had a way to use software and automated dampers in the floor vents to allow each room to be its own heating zone.  Found a link to their site --- https://www.ecoventsystems.com.  I wouldn't have been as impressed if Rich hadn't been so excited about it.  I tend to be sceptical of software based solutions for such physical issues but Rich, after upgrading a house with the Ecovents inventor and talking with him about concerns, was even more enthused than he had been at the start.

As an aside, what an extraordinarily beautiful garden you have, even from above!  Well worth preserving.

Thanks, Lulee! You’re almost a neighbor, so drop by if you’re ever heading to the seacoast!

I saw that episode of TOH but totally forgot about it until you mentioned it. I remember being slack jawed while that segment was on!

[Lulee]

Thanks for the offer, trachma.  I rarely get to the beach these days but perhaps when I FIRE.

Please update us on how things go.  The Old Farmer's Almanac has threatened us with a very cold, snowy winter this year which hopefully turns out to be wrong.  Hate to think of you and your family struggling through such weather without this solved (raising teens is enough drama for any sane couple to deal with IMO).

[mwulff]

How about an electric heat-pump for the second floor. To alleviate the need for forced air at that level? I'm not sure it could work, but it might be worth considering.

And as a side bonus it can cool the 2nd floor in the summer.

[trachma]

Ok, so I got all the specs on our new furnace and used the oil nozzle size to help calculate the oil usage per hour to heat the house to various temps (65, 61 and 57) when it’s 32 outside (nothing fancier than sitting by the floor register with a stopwatch while I watch TV for that). I also did some rough math on the space heaters, and our current price of oil (*very* low!) makes it a no brainer to put away the space heaters. When the kids move out and we just have our room to heat, those numbers are likely to change.

It could also change based on fluctuating electricity and oil prices, of course, so I’ll probably run the numbers each year with new rates. If your’e really curious about the math (prob. not!), I wrote about it here: <url>http://portpotager.blogspot.com/2016/12/trim-fat-tuesday-furnace-vs-space.html</url>

Thanks for all the great ideas!

[aerofreaky`]

If the building can take the weight, beef up the subfloors, pour a thinset with radiant lines and add a heat source. Finish the floors later... tile, laminate, etc...