room size and btu output

Brad White_149

and to answer your questions:

You need to know if the walls are insulated, what your desired indoor and outdoor design temperatures are. Where are you located?

What affects the heat loss is the area of glass, wall, roof and crawlspace which divide heated from unheated areas including the outdoors and the crawlspace. Does the glass have storm windows or is it Low-E or double-pane?

Ask yourself what holds heat in? You cannot guess, you have to measure.

The crawlspace would be warmer than the outdoors -one hopes!- and this is calculated separately. Absent other information, I would also assume one air change per hour of infiltration. 1.5 of you think the room is leaky.

I would not subtract the volume of cabinets or count them as insulation for heat loss purposes. The only affect cabinets and islands have is if you use radiant floor. They cut down on the area available to use for that.

Hope this helps-

Brad

m_6

room size and btu output

How does one determine what size radiator a room requires? I have a 21'long x 7'wide x 9'high galley kitchen and want to install a water radiator that will be hooked back into the house's system. What size do I need? Do cabinets and counters affect the square footage of the room, thereby not requiring as big of a radiator? I also have three outside walls, a crwal space underneath and it faces north which makes for a very very cold room.
Anyone have advice?

Uni R_2

Online and free...

Try the Hydronic Explorer tool from Slant Fin. It's quite good!

big bill_3

i would size a panel radiator that would deliver 8000 btuh and a non-electic zone valve, this room could require alot on a cold windy day

m_6

radiator size and btus

Thanks for your help Brad.
I just took more measurements.
The crawlspace is roughly 9'x7' and about 3' high.
My window area is 639.5 sq feet (7674 sq. inches, I measured in inches).
I'm located in the Northeastern US. I'd like it to be 65 degrees.
I would say the addition has insulation but I'm not sure about the condition of insulation in the original part of the kitchen. Half the kitchen has a second floor above it.
Im not sure I understand what you meant by "one air change per hour of infiltration. 1.5". It is leaky.
I ordered the Slant-fin free software but I'm going to a dealer Saturday morning and had hopes of bringing home a radiator.
Something else I've been asked is how thick the walls are. It's a 90 year old home with a 1960s addition. What do you make from that?

Uni R_2

Wall Thickness

The thickness should be fairly obvious at windows and doors. As for what's in the walls, try taking plates off electrical boxes and peaking to the sides. looking where anything passes through the wall will also help.

Brad White_149

Caught my breath for a second!

Simple divisor error- your 7674 square inches works out to a more merciful 53.3 SF of glass. (7674/144 not 12) Whew!

I would think at worst the wall will be 2x4 construction but where it gets dicey is how much the windows cut that up with more framing per unit area than insulation. Having 20% glass is one thing, you might have 20% framing. If you have 50% glass or less glass but broken up into smaller units, the remaining wall might be 50% framing which degrades the wall.

Is there a roof or is it below heated space? If so is it insulated and to what degree?

Is this kitchen the 1960's addition?
How cold does it get outside? Northeastern US covers a lot of ground. How does zero sound?

If the 21x7 room has three exposed sides, 7', 21' and 7' by 9 feet high, that is a total of 315 gross SF. Less 54 SF of glass this leaves 261 net SF of wall. If this wall has 3.5" of insulation and perhaps a degraded R value of 10 with framing.

Let's say the glass is double-pane or has storm windows at least. And let's throw in a footprint-sized roof with the same R value as the wall just for giggles.


I get, with a 10% safety factor thrown in, 8,100 BTUH.

WHO GUESSED 8,000?? Nice work, Big Bill!

No real harm in reasonably over-sizing a radiator so long as you can control it with a TRV (recommended in a kitchen).

My $0.02

Brad

Brad White_149

Good Shooting. See Above (NM)

D107

good time to do a full heat loss and gain calc, eh Brad?

From what you and others have said over and over on the wall, having e.g. 2x the required radiation is great for mod cons, outdoor reset, etc. So if he matches his new rad to not only room requirements but to the same ratio of overradiation (assuming that's the case) then he's in good shape right?

Thanks,

David

Dan Joyce_4

21*7 room,9*7 crawl space

Mr.M you have issues.
The above post are great,but you have install problems.
#1 I'll bet in the crawl space you can see outside daylight.
#2 You have no acess to 7*12 feet of your room.
#3 Kitchens are tough because of lack of wall space.That's why kick space heaters are made.
#4 One heater,radiator or panel. I'll bet you'll have plenty of cold spots and really cold dishes.

It might be time to find a pro.

Dan Joyce

m_6

boy oh boy!

Oops on the division error. Glad I included those inches! I had a feeling I would do something like that. Can you tell I'm a first timer?
I spoke with a local plumbing outfit and from my description (this was before I measured the windows) in his estimation, worst case, would be 4500 btus, according to the charts. Brad, you mentioned oversizing. So if I bought a radiator that was too big it wouldn't be that bad? Would it be negligible in heating costs?
To answer more questions:
The kitchen comprises both the 90 yr old kitchen and the addition. On top of the old section is the second floor bathroom. The 1960s addition is the 9' with crawlspace. Under the old is the basement where everything is going to connected up from.
Northeast means New York State, upper Hudson Valley. We get zero and below a few times a winter. Temps hold just under freezing for weeks at a time.
In the addition there are two double paned windows, a small single paned window and a back door, half glass (storm door). The 90 year old section had two double hung, single paned drafty windows but they have storms.
Is TRV the "non-electric zone valve" that was mentioned earlier? I'll this valve to the guy who's doing the job. I'm trying to spec this out all myself and go buy it to save money.
Thanks everyone! I really appreciate your advice. Learning a lot. I will be grateful for any more you would like to add.
-Meredith

Brad White_150

Meredith-

You are doing very well!

There is no harm in over-sizing a radiator like we are talking about, so long as you install a TRV which will limit the output based on space temperature. It will put out what is needed.

Yes, the TRV is the same thing as a "Non-Electric Zone Valve". They have also be called NERV's as in "Non-Electric Radiator Valves" but that acronym got on everyone's nervs so to speak. TRV seems to have taken on a certain cache'

We took some (qualified) guesses on your behalf, but if the assumptions seem reasonable, you are good to go. 4500 BTUH? I cannot justify that without more information.


Let us know how you work out, would you?