Basement Insulation

Kjmass1

I'm trying to get a rough estimate for finishing off my basement and looking in to my heating and insulation needs to price it out. I'll get a manual J done before I proceed but looking for a little help estimating my heat load for the basement only. Currently 1 pipe steam system. Pipes are insulated.

1940's basement is almost 1100 sqft but I'm going to finish off 700 sqft and the rest will be the boiler/utility room. 7' ceilings (I know, not ideal), and the foundation is 90% under grade. Zone 5/Boston climate. It was 25 degrees the other night and the basement was 61, so it stays pretty warm. I'm planning to do closed cell on the walls- is it worth it and would R-21 be overkill?

There are currently 2 ceiling radiators in the space I'm finishing- I put them at 9k each or 18k BTU total...I put a hoffman vent on them and let it run overnight and the room moved up to 63 so if I opened up the vents they'd definitely put out some heat. My only concern is having them run all the time- slowing steam to the rest of the house- it would be nice to maybe to install some heated floor mats to supplement and lessen the load and warm up the slab.

4 mats @ 30 BTU/hr in the main portion of the room would add about 10k BTUs...but pricey.

Any rules of thumb for basement heat? 40 BTU/hr would put it around 28K BTU, volume x climate zone would be around 25K BTU. I'm assuming if I insulated the foundation walls and added 10K in floor mats it I would be in pretty good shape?

Any advice would be appreciated.

Kevin

Jamie Hall

Are those two big basement radiators at the ends of mains, or close to them? If so, they are very helpful to balance the entire system, and putting bigger vents on them will have much the same effect as putting bigger main vents on the system as a whole.

In other words... use them!

Kjmass1

Yes- they are both at the end of the mains. Mains are vented well with Gorton's but that is an interesting idea. I'll throw some D vents on there and see how it heats it up. Thanks!

kcopp

If you insulate the walls and seal up any cracks you prob will not need heat.
What are the walls made of?
If its a stone foundation you need to be careful.

Kjmass1

I believe they are poured concrete- definitely not cinder block or field stone.

ChrisJ

Seems like an odd idea Jamie, especially if you don't want the heat.
Skip the radiators and use the main vents.

Kjmass1

I'm assuming he meant that using the radiators would add a little bit of additional venting to the end of the main...at the expense of steam filling up the basement rad before heading up stairs.

vaporvac

My understanding was that the OP wanted the heat, but was afraid using the ceiling rads would steal steam from rads on the main floor. Thus, his consideration of a floor mat heating.

"There are currently 2 ceiling radiators in the space I'm finishing- I put them at 9k each or 18k BTU total...I put a Hoffman vent on them and let it run overnight and the room moved up to 63 so if I opened up the vents they'd definitely put out some heat. My only concern is having them run all the time- slowing steam to the rest of the house -it would be nice to maybe to install some heated floor mats to supplement and lessen the load and warm up the slab."

Kjmass1

vaporvac said:

My understanding was that the OP wanted the heat, but was afraid using the ceiling rads would steal steam from rads on the main floor. Thus, his consideration of a floor mat heating.

"There are currently 2 ceiling radiators in the space I'm finishing- I put them at 9k each or 18k BTU total...I put a Hoffman vent on them and let it run overnight and the room moved up to 63 so if I opened up the vents they'd definitely put out some heat. My only concern is having them run all the time- slowing steam to the rest of the house -it would be nice to maybe to install some heated floor mats to supplement and lessen the load and warm up the slab."

Since my boiler is grossly oversized I'm not too concerned about it- but given that the room will be used sporadically, it seemed like there could be better solutions vs running them all the time. Heated floor mats would take hours to heat up anyways so it's not like I could just turn the thermostat up when I wanted to use the room.

A hot water loop off the boiler is also an option but figured that would be pretty pricey. Not too keen on electric baseboard, and ventless NG space heaters don't seem safe either.

I'll increase the venting tonight and see how it reacts.

ChrisJ

You can add more main vents if more venting is what you want.
If your boiler is grossly oversized, that's another story.

I'd consider running the radiators then but a proper sized boiler would be a lot better. Have you looked into a 2 stage gas valve?

Kjmass1

Main venting is in pretty good shape. Probably takes 2-3 minutes from once steam is going...but could use another gorton to max it out.

Boiler is 192k in/152k out. My radiator EDR is around 363 and that is with the basement included. It's 20+ years old and would love to get it down to an IN-5.

Jamie Hall

ChrisJ said:

Seems like an odd idea Jamie, especially if you don't want the heat.
Skip the radiators and use the main vents.

There are many ways to set up a steam system -- as we all know! One of them used big radiators in the basement at the ends of the mains. They do add heat to the basement, true, and that is sometimes useful. However, until their vents (or traps, on a two pipe system) close, they also represent a very low pressure or vacuum point at the end of the main, which can significantly increase the initial distribution of steam to the end of the main. Yes, they can be eliminated -- but it will take a lot of main venting at the same location to do the same thing.

ChrisJ

Jamie Hall said:

ChrisJ said:

Seems like an odd idea Jamie, especially if you don't want the heat.
Skip the radiators and use the main vents.

There are many ways to set up a steam system -- as we all know! One of them used big radiators in the basement at the ends of the mains. They do add heat to the basement, true, and that is sometimes useful. However, until their vents (or traps, on a two pipe system) close, they also represent a very low pressure or vacuum point at the end of the main, which can significantly increase the initial distribution of steam to the end of the main. Yes, they can be eliminated -- but it will take a lot of main venting at the same location to do the same thing.

They represent a very low pressure point only after steam hits them on a single pipe system. By that time, you don't want any more "main venting"

That low pressure point will be sucking steam from radiators a person actually wants to heat.

JUGHNE

You wanted those Hoffman vents upside down to stop the heating? Or did I miss something in the above text?

Kjmass1

I had turned off the rad at that point

Fred

He's finishing the basement and considering adding a supplimental heat source. That's what his post is about. I say leave those radiators and if he does the insulation he is thinking about, he may not need anything else. Has that huge cycle start-up venting capacity and the heat source for the finished basement. What more could you want?

Kjmass1

Any guesses on how many BTU's a steam main puts off? I wonder if I took the insulation off how much that would add.

I agree- might make sense to insulate and then see how the radiators work- although I probably won't get to that in the summer.

I just don't want it to be underheated and feel cold being on slab.

vaporvac

Removing mains insulation is NOT the way to go, unless you don't care to heat the upstairs, as well. Doing so will drastically increase the rate at which the steam condenses, resulting in more gas usage, longer run times, and rads at the end of the line not heating. Please don't do it.
There's no reason other than expense not to use something to heat the slab, but perhaps that could be done later as those ceiling rads should put out quite a bit of heat. You could also try something reflective above them.

Jamie Hall

Don't take the insulation off the steam mains! It upsets distribution, and allows much more condensation in them, which they aren't intended to carry. Not a good idea!

Jack M

In Mass you may need to look into adding a "fan in a can" if the basement is insulated and air sealed. The burner needs replacement air.

Kjmass1

null

Never heard of fan in a can- thanks for the heads up. Does this apply if I just insulate the rim joists or entire foundation wall?

Now I need to shoot a bunch of freezing air into my utility room? So much for insulating but I understand the rationale.

SWEI

Kjmass1 said:

Now I need to shoot a bunch of freezing air into my utility room? So much for insulating but I understand the rationale.

Assuming you get a properly trained combustion tech, it will not be a bunch, but it will be enough to keep the burner running clean and safe, and only when the burner is running.

Kjmass1

Hatterasguy said:

Kjmass1 said:

Any guesses on how many BTU's a steam main puts off? I wonder if I took the insulation off how much that would add.

Your boiler is way oversized for the connected EDR load. Therefore, removing insulation from the mains won't have the slightest impact in the capability to heat the remaining rads.

You have to condense all the steam anyway and the mains see every drop of it so some condensation in the mains directly, instead of the rads is not an issue.

What's the length and diameter of the main in the area you wish to heat?

I believe it is 2" black pipe, 2 3/8" outside diameter. Approx 20' would be in the finished area.

ChrisJ

Removing mains insulation, or running radiators right next to them..... not really seeing a difference here. Other than I'd expect those radiators to eat a lot more steam.