HL for a Church?

Unknown

going to measure things-up tomorrow(hopefully), and work on them this weekend. Just wondered if I should bring-in a professional engineer for this kind-of sizing stuff.<BR><BR>Dave

Unknown

This place has,

3 old FA gas units in a dirt basement and no A/C. Thinking of going with AH w/A coils and DHW, fed with M/C boiler(s). Thing is, likely these FA units are super oversized as they run the church cooler when not in use, but when called-on its got to heat-up quick. Anybody have any experience calculating HL on a place like this?

Dave

Brad White

Have you calculated a basic heat loss

yet, Dave? Do you have a take-off of walls, roofs, windows, materials?

No different than any other space but for pick-up factors that is as much art as science. It can be an add-on of some percentage, 10, 15, 20%.... this is how older systems became over-sized so start with a good calculated heat loss. Take into account ventilation air for the population too. Whatever your local code dictates.

In the case of using Mod-Cons, go for 4-row heating coils or deeper and variable speed blowers. A pair of boilers if needed to meet capacity might also be a blessing, allowing low and high capacity operation with pick-up in the bargain.

But the basic approach is not much different than any other space.

Brad White

Start there

and take it as far as you can and we will see what we can do.

A good calculation set run before this forum as a sanity check will be a good thing.

Unknown

Thanks Brad,

was hoping I could count on you, when I get those #`s, I`ll be back.
BTW-You mentioned ventilation-air and local codes?, don`t forget I`m in the Canadian version of "Oz" here. Permits are not even required, but we do have a "Hector The Inspector", so I`ll be on my own.

Dave

tim smith

Church heat

I have worked a fair amount. When you mentioned modcon, I thought about another job that we had done ( not in church) and used the hot water boost temp on the boiler to get full output when needed. Maybe oversize your coils for air handlers and use 2 stage thermostats, 2nd stage bulb to kick unit into hot water boost feature to bring up temp from the cold set back temp and then would modulate down to normal curve temp about 1.5 degrees befor satisfied. I would probably guess you may need to oversize by 20% unless they have a very set schedule that you can program stat for, which few I work on have a consistent one. Just a possible thought, Tim

Noah

Church HL calcs

Good idea Tim, a great option to consider as I progress. Firstly though, I can come-up with a factor for the 24" stone ex. walls,,but having trouble finding something on the leaded-stained-glass windows, this place is 1880s vintage and has what appears to be clear "plexiglass" attached over outside(likely added in the 70s), I would think the factor for these would be quite unique because of their dark-colored nature.
Any ideas?? Brad?

Dave

Brad White

Stone R Value

Depending on the type of stone, here are some values, Dave:

Limestone or Sandstone at 180, and quartzitic sandstones at 160, 140 and 120 lbs. per CF:

R per inch = 0.01, 0.02, 0.04, 0.08 respectively. Your 24" wall would have a total R value of 0.24, 0.48, 0.96 and 1.92. Don't get exited now, OK?

For granite at 180 PCF, 0.03 per inch or 0.72R. Big Whoop.

Naturally you would add your 0.68 indoor and 0.17 outdoor air film values to this to arrive at your whopping 1.6 R value or 0.625 u-factor. About as good as glass block but lets in less light.

I could find no data for "Rock of Ages" by the way...

If the wall was in fact built in two sections with an air space or terra-cotta, this very well could double the R value.

For the glass (stained glass with Plexiglass), I would take those at a u-factor of 0.68 if they are well-sealed. If the fit is sloppy (evidence of condensation between), I would take them at halfway between that and single glass, maybe a u factor of 0.90 or so.

clammy

churches

dave ,in the past i have done a few older churches and beside the sizing which i had nothing to do with what we did do is used a 3 a/h and a 3 stage stat ,all the fans ran on any call for a/c and all 3 units where stages for a/c the churched ended up with 15 tons of a/c and it's been about 12 to 14 years since we did the job but all 3 original condenser are still there and running and i have not heard of any complaints except that it was beautiful inside and the church always seems packed on sunday .peace and good luck clammy

Noah

Ok Brad,

with EXTREME difficulty I seem to be narrowing things down, I used an outside temp of -5ºF and an inside temp of 68ºF, but the infiltration factors really make my final #s swing, if I use 1.5 ACPH, I`m very close to the "net" of the existing eq., but I don`t think this is enough,,any input in this area?

Dave

Brad White

Infiltration Wildcard

Hooboy.... Always a SWAG, even with a blower door test.

I would do it a couple of ways...

Stone tends to be fairly air-tight and homogeneous as opposed to disparate materials such as wood frame meeting masonry or the modern standard of construction. This is of course good news for you.

There may also be fireplaces, chimneys, attic ventilators (much like a barn) and of sealing standards unknown.

What I would do:

1) Quantify all potential points of leakage. Operable doors I would take at 1.0 CFM per foot of crack and windows at half that for the operable perimeters. Do that sum for all fenestration and see what you get. If you have an attic ventilator (any filigree medallions on the ceiling as a tell-tale?), check them out. If they do not have dampers, see if such can be had. Summer a good thing, winter, not so much

2) Take an "air change heat loss" at 0.25, 0.50, 0.75, 1.0 and 1.25 ACH. See what you get and compare it to the crack method you did above. 1.5 ACH sounds high to me. If I had to punt, I would go between 0.75 and 1.0 for a large building. The larger the building the smaller the number. Again, experience, not borne out by any post-design testing unless a lack of complaints is considered a compliment.

3) Can you get a blower door test? Even a single-point test of ACH or CFM at 50 Pascals will get you a ballpark number even in summer.

All told, I am seeking to triangulate to find the best number of all, either taking the worst case or averaging them. Even after all this we are still taking a guess, but the blower door is less of a guess than any of them.

You can see how systems can be grossly over-sized given the range of infiltration possibilities.

The "Good News" (huh?) in all of this is that the walls are so poor in the insulation department that the infiltration will be a relatively small percentage (often 25% or so of total heat loss). Hey, there is another point of reference for you.

You can see in a better insulated structure how infiltration, if kept the same, will amount to half or more of the total heat loss as a percentage.

Thoughts?

Brad