Heat loss for churches

Don Walsh

I have been asked to quote replacement boilers in several area churches. Most of them have huge boilers that are fuel inefficient and probably grossly oversized, but I need to know for certain that they are. I am at a loss as to how I should calculate the heating load in cathedral type buildings with vast expanses of stained glass windows, and unknown insulation values of the structure. Anyone have any ideas?

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Wayco Wayne_2

What kind

of heat emmiters are they using?

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Firedragon_4

Forgive me for over

simplifying this, but it's still just 'a box in need of heat'. A good program should take care of windows, doors, etc.

Height is squared off to make it easier, you won't be off and oversized by that much, fact! If you can always recommend ceiling fans.

Remember occupancy, the pastor should be able to help you with that. SETBACK thermostats are a MUST.

Open a wall somewhere out-of-the-way or figure there's not much in the wall if the building is over 30 years old.

Pray, you're in the right place! :-)

DanHolohan

If it's steam heated

you may find that the output of the installed boiler and radiation are much less than the actual heat loss of the church. The Deadmen often did this in religious buildings to set up a mini-atmosphere within the building. The undersized radiators would provide radiation, and also convective currents that didn't rise all the way to the ceiling. The air near the top of the church stayed cool all the time. When you add ceiling fans to these buildings you actually increase the fuel useage during the winter because the fans stir the cooler air into the lower, heated air, causing the overall air temperature to stay below the thermostat's setting. That's why you don't often see those fans running during the winter.

Thanks to Andy Rudin of Philadelphia's ICE, who figured this out during the 70s.

Steve Minnich_1

This is important

Don't forget to calculate ventilation air, recommended air changes per hour, etc. This plays a large role in both the heating and cooling load calc's.

Many commercial buildings require 15 cfm/person of ventilation air which has a HUGE impact on equipment sizing, including the boiler.

But with churches it is a little different because of oocupancy codes/laws/rules. Because many churches are at full occupancy only a couple of hours per week, most municipalities will require only 7.5cfm/person. This translates to a much lower "people ventilation load".

I'm installing multiple boilers in a church right now in which the particular village we're working in recently switched from International Mechanical Code of 1998 to IMC 2003. This code change dropped the 15 cfm to 7.5 cfm and and reduced the size of my boilers and high velocity AC's considerably.

Hope this helps.

Steve Minnich

hr

Infiltration

is the biggest number to pin down. Seems a church with large open entry doors would need a system that responded quickly when all are inside. Certainly high mass iron, or radiant slabs fit this bill nicely. Radiant energy travels at the speed of light!

Air changes and introduction of tempered air are also important in any public spaces with large people loads, as Steve cautions.

Might be worth a sit down with a designer or engineer versed on conditioning spaces like yours.

hot rod

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Boilerpro_3

About 90% of my commercial work is churches

Even though out in here Rural Illinois they tend to be much smaller. As Firedragon said, do some digging into the construction of the church and do your basic heat loss calc for exterior surfaces.

As with any larger structure, infiltration can only occur near outside walls, so I assume only the outer 15 feet of the structure as basis for the air changes per hour calculation. Also, when figuring infiltration air changes per hour, most sanctuary structures are much more airtight than the typical structure. The ceiling is a continuous, nearly airtight sheet of plaster. In contrast with a typical home or structure with many partitions breaking the airtight surface of the ceiling, there are few or no interuptions in this boundary in a church sanctuary, so there is very little air leakage at the ceiling. Little air leakage at the top means much less air coming in at the base due to a reduced stack effect through the space.

Most church windows have some exterior covering. I usually figure the R-value of windows about halfway between single pane and double pane glass due to the fact that the air layer between the windows is probably not very stable due to the leaky nature of old leaded glass windows with brittle caning.

If you use a hot water system with outdoor reset, do not use ceiling fans. I have had some sharp parishners check the air temp on a convection heated sancuary with reset on the system and have found the air temp to be within 2 degrees at the ceiling, versus about 5 feet off the floor. Under these conditions all the fans do is create a cold draft for occupants.

In my opinion, if you have two pipe steam system with cast iron rads, you may still not want to use ceiling fans since the air is not heated to as high of a temp as with one pipe steam, since the heating is spread through the length of the top of the rad.

With one pipe steam, you probably get alot of superheated air coming off the completely heated hot end of the rad, so ceiling fans are probably a good idea.

Also, definitely use setback stats with deep setbacks (recommended is 45F by the Interfacith Coalition on Energy). This protects the furnishings and pipe organ from very damaging drying by heated, but not humdified air when the space is not in use. I have seen relative humdities of about 15% in church sanctuaries in typical winter weather when heated to 65F. This will destroy a million dollar pipe organ in a few short years (contact the American Guild of Pipe Organ Builders about this).

Hope this helps


Boilerpro

Don Walsh

Okay, a few details

I'll deal with church "A" in this post. It is a 60 year old brick faced building that is 175'deep x 80'wide x 54'high. The exterior walls are two courses of interlocking bricks at the core, with a brick facing added to the exterior, and glazed tile brick on the interior. The interior tile extends 6' up the wall, and from there it becomes plaster finish to the ceiling line. The ceiling itself is tounge and grooved 2 1/2" x 6 planks with a slate covering on the exterior. No other details of the roof are available.

There is a seperate 150 ton cooling system serving 6 air handlers. They are adamant about not heating with forced air because of noise issues. (Older priests, soft voices, no amplifier systems)

All entry doors (3) to the sanctuary have airlock type vestibules and are sizable areas unto themselves.

The biggest complaints registered over the years has been that the sunny side of the church overheated while the shaded side was always too cold. I am proposing to replace the system with commercial baseboard on the perimeter walls and zone it from side to side at the very least.

All the nomenclature from the existing boiler has been removed over the years, so knowing what is currently there is at best a guess-timate (somewhere around 2 million btuh based on burner sizing)

The building has a full finished basement used as a fellowship hall (read that bingo parlor) that is 60% earth embanked, but with walk out entries (2)to the ground level parking lot areas.

My primary concern has been the height of the structure when calculating heat loss. A preliminary work up gave me only 1,200,000. My gut feeling is that it is too small a number.

There is no existing mechanical air ventilation system. The building had been heated for 60 years with a steel pipe in concrete radiant system. The steel piping has finally rotted and the custodian kept feeding water to the boilers daily to try and maintain heat all of last winter. Well, that destroyed the boilers in short order.

The windows are huge, 10' wide by 30' high ending in arched tops,and are of single pane stained glass. There is no exterior protective covering to act as a possible air space. I have suggested adding a protective covering, but they have concerns about the appearance.

My initial thoughts have been to manifold several condensing boilers with outdoor reset and using P/S piping to add and control multiple zones to the areas being served. There is currently one thermostat for the entire building!

Occupancy during mass is the next big item, at peak times there are 800 people in the building at lesser times as few as 150. There are masses daily starting at 5am and running hourly until 10 am weekdays. On Saturdays, masses start at 4pm and run until 8pm in the evening. Sundays they start at 5am and finish at 5pm. To attempt to calculate that load with such wide parameters is also a challenge.

I do have the local Burnham rep coming in this Thursday morning to have a walk about, so hopefully he has had exposure to these types of structures in the past. I only have one shot at getting this right, as small as this town is, a mistake here will be fatal to my business reputation and future.

Thanks everyone for your comments, I really do appreciate the assistance I receive here on "the Wall".

Grumpy

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jackchips_2

Grumpy,

have you contacted a Mechanical PE?

When we replaced our oil boiler, to natural gas, over 15 years ago, in an Italian Gothic Church with 70 foot center height, I sought out an engineer from the congregation who sized everything for us.

The system has worked fine from day one.

Good luck.

Don Walsh

Engineer

Yes, we have a PE who is working on the project for us. I am by nature one who needs to "know everything" about the systems I install, so as a result, I tend to double and triple check everything that I get involved in. I am wanting to run a complete heat loss on this facility so that I can compare it to that which the engineering firm develops. I mentioned before that a mistake here would be of very serious consequence to my company, so I tend not to just accept things at face value. The engineering firm would of course be responsible for errors in their design should any be made (doubtful), but that won't help me if I'm damaged by any possible mistake made on their part. I know, I'm paranoid, but I always have and will be as long as I'm putting my name on the finished product.
Grumpy

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Boilerpro_3

Good thinking

and engineers do make mistakes or, at least, very poor choices. The engineers who designed the heating system for my local high school specified a 14 million BTU/hr input boiler.... the heating load is about 4 million.

Your 1,200,000 load may even be high( assuming no forced air ventilation load). I did the heat loss load calcs for a 600 to 800 seat sancuary, basement social hall(together 30,000 sq ft floor area) and 15,000 sq ft 3 story 1950s (read R-2 walls) education facility and the load was about 750,000. The facility had heated with a 1,200,000 input Kewanee Type R for nearly 30 years. The new staged boiler heating plant worked great last winter in the converted steam convector to hot water system. I heard they dropped the midwinter fuel usage about 50%, despite the coldest winter in 12 years, probably about 60%or more for the season.

Staged boilers, with a lead condensor or two, would be my choice.

BTW, watch the forced ventilation loads. It appears that most engineers figure the building load plus ventilation load and then add a 50 to 75% pick up factor. This is doesn't make sense to me. The ventilation system will only be running once the space is occuppied, so why do you need to add a pick up factor to the ventilation load AND the heating load?

Also, the heavy loads at entry doors due to doors opening and closing really does not need to be added to the boiler size, since the pick up factor will drop out once the building is ready to be occuppied. Also if the building is in use, lighting, people are reducing the internal bulsing loads, displacing a portion of the heating load. All of this additional capcity will be available to provide the added heat for the entries.

I also would not size the system or heating plant for greater than 25 to 30% space heating load pick up, even with 45F setbacks, because if the spaces warm up too quickly, you may have 72F air, but everything in the space is still cold and you end up with the "cold70" syndrome due to very low Mean Radiant Temp in the space. Check out how the Honeywell Chrontherm stats recover a space.....they limit how quickly the space will warm up to help prevent this problem.


Boilerpro

Mike T., Swampeast MO

Stained Glass Window Infiltration

I tried to find info on this but it was really sketchy.

Having made a few I do know that a putty that seems very similar to plumber's putty with lampblack or similar added is forced between the glass and the lead--both outside and inside if you're doing a good job.

Barring impact, improper support against wind, or centuries, the putty tends to last very well. From what I read most of the infiltration (water mentioned most frequenty, but of course air would be coming through as well) occurs around the edges where the window meets the frame or sash.

Also from what I read, things similar to storm sash have to be very carefully and specially designed so that the stained glass panels, lead, putty, etc. don't deteriorate faster than normal.

Since I guess that those big stained glass panels are fixed, I'd think you would be safe considering them as single-pane operable (say double-hung) metal sash when it comes to infiltration and "insulation". This does assume that they're in decent shape. If, like many, there are numerous cracks and even some holes, I'd start revising infiltration upwards.

Wayco Wayne_2

Boiler pro

stole my thunder. I did a church where we staged boilers and had a lead condenser boiler. Works great and saves money. WW

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Boilerpro_3

Yep, staged boilers typical save at least 40%

when combined with automatic setback controls and boiler reset. In the dozen or so churches I've done in the past, the smallest savings was 35% (the ventilation systems had previously been out of use and now were on line) the greatest about 60% in a steam to hot water conversion and taking the light switch operated snowmelt system off line. However, out of all the churches I've done, I have only been able to use one lead condensor configuration. So those 40 to 60% savings were with the use of simple atmospheric gas fired boiler. Using more condensors would be great, oh course ther still seems to be the problem of much more expensive maintenance that appears to largely offset the money saved due to reduced gas use.


Boilerpro

John R. Hall

Bringing it back

I asked Dan about using some of the comments here for an article I'd like to write on this subject for The News. If you'd indulge me, please answer this:

1) How do you "market" your business to churches, i.e. word-of-mouth, advertising directly, telemarketing?

2) Do church elders "typically" keep their HVAC equipment well-maintained? If not, are there any horror stories?

3) Is it a good "niche" market to work in?

4) Any special additional training you need to estimate a job?


Feel free to e-mail me at johnhall@achrnews.com with answers or additional comments.

Thanks much!

John R. Hall

Bounce to the top (NM)

Weezbo

of interest.....

John R. Hall

Thanks

Great story idea. It kept growing as I got some of our New's consultant contractors involved. I wrapped up the story and included a sidebar article based on the information that Dave gave about church "A". Maybe our readers can offer some ideas on how to size the job, too.

Thanks again, Wallies, for the inspiration!

Boilerpro_3

Cool!

Sounds like I'm hitting the big time!

Boilerpro