Heat from pipes in crawl space heat water lines?

Bigriver

I have a small commercial building in Minnesota. It has hot water baseboard heaters. The space it heats is about 1000 sq ft and the lines run in a crawlspace which is largely below ground. The water lines for the bathroom also run in the same crawl space. I am considering switching out the boiler to a heat pump or ducted forced air. Whichever way we go I am concerned about the water lines in the crawlspace freezing up. Do baseboard supply lines give off heat to heat these water lines in the crawlspace above freezing? The baseboard supply lines and water lines are uninsulated. Happy to give more specific answers to questions if you have them.

hot_rod

Maybe start with sealing and insulating the crawlspace? Any heat you put down there will just run up the fuel bill. The cold transfers up to the living space, driving up the heat bill also.

There are companies around that specialize in crawl insulating.
I bought some rolls of Insultarp and did my own, the ground right up to the floor joists. Spray foam the rim joists around the perimeter and the plate to foundation, which is another air leakage spot.

You just need to keep it above freezing, but the warmer it stays the less your heating bill will be. If the footings are below frost level you should be able to keep the space above freezing. Any crawlspace vents need to be covered for winter, but may not be needed if you get an air tight seal.

Got radon issues around there? Another good reason to insulate the crawl from the living space.

Larry Weingarten

Hi, Is it a vented crawl space? If so, have you considered a sealed crawl? Sealing it will help make it warmer… or should. More specifics would be helpful. Do you have measured temperatures from the crawl?

Yours, Larry

EdTheHeaterMan

To answer your question directly, YES the heat from uninsulated heating pipes do add some heat to your crawlspace. Depending on many factors, removing that heat may tip the scale to a frozen potable water pipe. The colder it is outside the more your baseboard heaters will be operating and the more crawlspace heat will also be generated. SO... it depends. you may have a problem that needs to be addressed if those baseboard radiators are abandoned.

Have you also considered the comfort of baseboard heaters compared to the discomfort of heat pump systems? 68° with lower humidity and fan air movement is not as comfortable as 68° with higher humidity and virtually unnoticeable convection air currents. The heat pump might not be as comfortable as your hydronic baseboards. So you will set the thermostat a few degrees higher to compensate. That will dig into your energy savings by about 3% per degree above your former thermostat temperature setting.

Just some Rambling Thoughts.

Mr. Ed

Jamie Hall

Let's step back a square here. What is your design outdoor temperature? If you are planning on an air to air heat pump, have you found one which will function at that temperature? If you are planning on a ground source heat pump, have you evaluated the extra cost? In fact, have you done your sums at all? Keep in mind that switching from one way of heating a biilding to another will not change how much heat is needed. A heat pump will save electricity, it's true -- if it works at your design temperatures, of course -- but the capital cost needs to be considered.

So -- the question is not will the pipes freeze (probably not, by the way, if you insulate the crawl) but have you evaluated why you are changing at all?

pecmsg

I don’t have an issue with heat pumps. I have them in my home. I do have an issue depending on them 
a) when the NE wind blows here on the Isl of long with single didgets. 

b) that heat pump is a lot more complicated then my Well McClain Boiler. 

C) if / When we loose power I can power that boiler with a Small generator!

Bigriver

Thank you for your responses. I'll answer some questions here. It is a sealed crawlspace below frost level. Unforuntately I do not have temperature data from the crawlspace. We are updating our HVAC because we have a grant to do so, otherwise I wouldn't be considering it at the moment.

I have one contractor saying that the supply lines would freeze without the boiler water lines and another saying, emphatically, that they would not freeze - adding that yes they give off heat, but not enough to make a big difference.

The commerical part of the building is closed for the winter, so the temp is kept in the low 50s all winter, if that helps. We would like to go all electric system if we can, the only thing that the uses gas now is the boiler. Obviously the goal is to have a cheaper monthly bill. At this site, the only gas appliance is the boiler. The service charge from the utility company just for having the gas come to $300/year - just under 50% of the gas costs, so a good savings right off the bat if we got rid of the gas. Not opposed to using it, though am opposed to paying higher utility costs, ]whatever is cheaper.

One contractor suggested using an electric boiler for backup heat, as that would use the infrastructure of the existing baseboards. If we are going with the thought that the water supply lines in the crawlspace would freeze without a boiler, would that mean that the electric boiler would need to run frequently?

Jamie Hall

You still haven't mentioned where this is located -- and it makes a difference. In some areas, yes an air to air heat pump will do the whole job -- although you should carefully evaluate its performance under cold outdoor conditions and use your actual electric rates and gas rates to see if you will save any money. You may not...

Under colder conditions, it may not, and the suggestion to use an electric boiler backup on the existing system is a good one -- except that straight electric heat is going to be more expensive than gas in almost all locations. You need to carefully evaluate the actual costs here.

Bigriver

@Jamie Hall I'm in Minnesota as I said in the post. In my repsonses I indicated we receive about 3-4 weeks where temp drops below 0, a couple of times each winter it will hit -20 or more. I know a heat pump with an electric resistance backup does work here, I have a heat pump with electric baseboard backup in a 1000sq ft apartment. The winter utility bills are not out of step compared to other places in our area. Though I do not have the data to say whether it produces cheaper heating bills as the heat pump/elec. baseboard was installed after I purchased the building and before the first winter.

If the electric boiler only needs to run when the heat pump's efficiency is poor than it seems like it will amke sense $ wise, though if it needs to run frequently to heat the crawlspace and therefore the water lines than I am concerned about the expense of running it.

Running the numbers as best I can using current rates it makes since to go all electric if you have an efficient system, however, the concern as stated in the original post are the water supply lines in the crawl space and whether they would freeze or not w/o the heated boiler supply lines running in the crawl space.

mattmia2

Where is the crawlspace in relation to the space that is not used in the winter? It could make sense to drain the plumbing if it is for the unused portion. Another option it heat trace tape and insulation.

Bigriver

@mattmia2 The crawlspace is below the unused winter space. Though above that is an apartment which has a tenant so I couldn't drain the pipes. So in order from down to up is the crawl space, unused space, and then the upstairs apartment.

Jamie Hall

Your electric rates may be comparable to LP or oil for a heat pump to be competitive for most of the year. It will not manage those nice chilly days which you get, or at least air to water won't, if only because it won't get the water hot enough for your baseboards to keep up if you air to water, or to make the air warm enough if you go air to air. Then you'll need the electric backup.

Even though it's just for a few weeks, however, be aware that that electric boiler or furnace backup is going to draw a lot of power. Make sure that you have enough amperage in your service drop and switchboard.

mattmia2

Be careful about where the pipes run through the space closed down for the winter too. if they run in or near exterior walls they might freeze on a particularly cold or windy day maybe when the people in the apartment are away and not using water for a few days.

hot_rod

Self regulating heat trace tape is near 100% efficient With insulation over it it would not need to run much to stay at 40F. in a sealed insulated space.

Minnesota has some of the cheapest electricity in the US. As @GroundUp has mentioned, electric boilers can be cost effective up there.
Any HP that multiplies the electric use efficiency helps make the case. 2- 3 COP may be possible under some conditions.

ChrisJ

pecmsg said:

I don’t have an issue with heat pumps. I have them in my home. I do have an issue depending on them 
a) when the NE wind blows here on the Isl of long with single didgets. 

b) that heat pump is a lot more complicated then my Well McClain Boiler. 

C) if / When we loose power I can power that boiler with a Small generator!

If I was moving to Minnesota, which I have tried to convince the wife to let us, I certainly wouldn't be considering a heat pump.

I don't know about other areas, but the area I'm interested in see's -40F actual temperatures.
I'm pretty certain no current heat pumps will work there.

Bigriver

@ChrisJ MN is great, the -40F ain't too bad either! I would not rely solely on a heat pump in MN anywhere, especially up North. Though a heat pump with backup heat will most likely be on par if not cheaper than natural gas/propane, even here in MN. The heat pump in the apartment with backup elec baseboard does great and bills are similiar to other similiar apartments that rely on gas. Have not done a super deep dive on the data, but enough to feel comfortable recommending it. It's the $ to install that is the barrier, if it's a new build or changing systems than it'd be a good time to do it.

ChrisJ

Bigriver said:

@ChrisJ MN is great, the -40F ain't too bad either! I would not rely solely on a heat pump in MN anywhere, especially up North. Though a heat pump with backup heat will most likely be on par if not cheaper than natural gas/propane, even here in MN. The heat pump in the apartment with backup elec baseboard does great and bills are similiar to other similiar apartments that rely on gas. Have not done a super deep dive on the data, but enough to feel comfortable recommending it. It's the $ to install that is the barrier, if it's a new build or changing systems than it'd be a good time to do it.

Thank you for responding.
What would you be using for backup heat, just resistive electric?

Bigriver

@ChrisJ Yes that's what the aparmtnet uses. Some people use a gas/propane furnace or boiler as their backup. Deifnitely more expensive to use electric baseboard heat, but it is used infrequently so that the whole systems still balances out $ wise.

ChrisJ

Bigriver said:

@ChrisJ Yes that's what the aparmtnet uses. Some people use a gas/propane furnace or boiler as their backup. Deifnitely more expensive to use electric baseboard heat, but it is used infrequently so that the whole systems still balances out $ wise.

How do people get by using LPG in such temperatures?  Is there a need to bury or heat the tank?

mattmia2

If i recall there are regulators that can use the liquid.

hot_rod

ChrisJ said:

Bigriver said:

@ChrisJ Yes that's what the aparmtnet uses. Some people use a gas/propane furnace or boiler as their backup. Deifnitely more expensive to use electric baseboard heat, but it is used infrequently so that the whole systems still balances out $ wise.

How do people get by using LPG in such temperatures?  Is there a need to bury or heat the tank?

A few factor in play as to when the LP no longer can vaporize. The large boilers I worked on in the mountains had vaporizers that needed to run when it got below the natural vaporizing conditions at the tanks.