how to do a heat loss on a church sanctuary?

ratio

Like the subject says. Appx 150' x 75' plus smaller chapels of to the sides, ceiling is a 14:12 roof about 50' high at the peak. The chapels, vestibules, & whatnot I can use the slant fin app & I imagine I'll get a usable number, but how do I account for the high ceiling? I could figure out the average height & punch that in, would that give me something close enough to work with? Heat source is radiant slab, with two hydro air handlers as supplemental, about 8k cfm between the two IIRC. With this setup, will stratification be an issue?

Tinman

For the sake of getting the exposed wall square footage, you can break each down by the rectangular part and then the triangular part - add the two together.
Exposed roof/ceiling combo you can get a fairly exact number on that too.
As far as radiant load, have you tried Uponor's ADS software?
If a load calculation hasn't been done yet, why has supplemental heat been added?

Tinman

A couple other things - The need for the ceiling height measurement is to have the second measurement necessary for exposed wall square footage AND the need for cubic feet in the winter and summer infiltration numbers. For me, I find it easier to do a church calculation manually rather than through software for the same reasons you mentioned.

SWEI

I work out the average height for each wall and then use the roof slope to figure out how much exposed ceiling area there is. You need to override the computed ceiling area that the program computes from the room dimensions.

ratio

Ok. I figured parts of this would be manual calcs. @Stephen Minnich, this is an existing building (50's construction), only work done since corner stone was laid seems to have been a replacement boiler a decade or two ago (5 section 211A, NG) and 10 tons of cooling was scabbed into each air handler-maintenance has been scattershot & mostly demand as opposed to preventative.

I've been slowly working on things, trying to improve efficiency & reliability. This is my parish (sigh!), so I'm willing to spend time & money to get a better job as opposed to a good job. I ASSUME that the engineering was good & that it did work correctly at one time. The heat is adequate, but I'm concerned about the longevity of the boiler since we crater the temp when the radiant starts, even throttling the flows manually to < 100° supply. You can see some of the NBP here.

Firecontrol933

Maybe it's time to plant the seed in the powers that be to look at adding a second boiler for just the slab that could also be used as an emergency backup for the main boiler.

The addition of a modulating 95% gas boiler to handle just the slab would save the church a lot of money in heating costs each year over what you have now.

I did a smaller church 2 winters ago that sounds and looks kind of similar to your setup and the addition of the condensing boiler cut their fuel costs almost in half. I was told they figure the fuel savings would pay for the project in approximately 4-5 years.

ratio

I'm the powers that be; at least if I wanted to do it Father would probably be on board with it.

I've actually given some thought to doing exactly that. After I get the heat loss done I should be that much further along, but removing that load from the boiler probably isn't going to help the sizing any.

Jamie Hall

Startification in a space like that is a big problem. I assume you do have some nice ceiling fans, hanging from the peak of the roof? We have in our sanctuary, and they do wonders.

I very much second the suggestion of putting the slab on a separate boiler -- save a lot of wear and tear on everything.

May I also, however, put in a word for the organ (I'm also a church organist...)? They really truly don't like wide temperature variations... and, of course, neither do radiant slabs. You can perhaps get people to minimize monkeyshines with setbacks...

ratio

(Ah, only parts of the organ left. A terrible loss to the parish, but not essential to the faith.) In any case, no ceiling fans, although again, I've been contemplating them. I'm not convinced of the essentiality of them, if the heat is predominantly radiant I don't know that I'll have too much issues with stratification. The returns are low, the supplies are ~15' - 20' high, throwing along the long axis.

The case for a mod-con on the slab is getting stronger. I've got quite a bit of work to do before I can do the maths on it, but as things stand now unless it's completely one sided I'll be gunning for it.

The slab isn't set back, it can't be, but I am considering outdoor reset as opposed to the current manual reset. There's good bones here if I can get it fleshed out right.

Jamie Hall

Do contemplate the ceiling fans. They are a bit of a pain to install (it's a long way up!) but they made a world of difference in our church, both in summer and winter. And they are really cheap... relatively speaking! And no one notices them -- get them the same colour as the ceiling.

Outdoor reset is your friend on the slab. Go for it!

Sorry about the organ, but it's a common enough tale.

ratio

How far down do the fans hang? I did a remodel in a Baptist place once, the fans were staggered so that they didn't appear in the video feed of the service, but that's not a concern for us. I'd need about five bucks of scaffold and a ladder to reach the peak; and move the pews to fit down the center.

Erin Holohan Haskell

@ratio, here's an article about the secret to heating old churches that may help you out. It covers radiant, lofty ceilings, ceiling fans, and sizing systems.

Let us know how it goes!

SWEI

Great piece, and I don't know how I managed to miss it.

Huge areas and volumes with little to no insulation plus intermittent occupancy makes for a real challenge. Bring it on.

ratio

Thanks Erin, more to think about. I'm to the point where I have to start proving stuff with math, the doing it is right around the corner!

nicholas bonham-carter

Do you suspect the boiler, with its 460k BTU's output to be oversized? Have you noticed any short-cycling when the system has come up to speed? Peerless give the option of the Mod-u-Pac Hi-Lo gas valve train which could solve some over size problems.
The return temperature could be controlled by different controls, and piping, and shouldn't the radiant floor be on for the whole time the building is in use, and not just for each service?--NBC

ratio

I'm unsure about the sizing. Playing the odds, it's oversized, but I've never sat there & watched it for a day to see how it's performing. I've got the kit to convert it to two stage, this summer I hope. The radiant loop runs continuous, but it's bang bang with the circ. When the pump starts, the boiler temp craters, 120° SWT according to the tridicator.