HEATING SYSTEM FOR A CHURCH 3

[Welchita]

HI Folks!

Suppose an existing church, located at a 40º North Latitude site above, I mean, a building with high and strong thermal inertia/material, and an open space as well.
How do you make an energy efficient approach to choose the type and how to design an proper heating system ? Also, the installation must cause/have minor implications for the building.

Shall we have some comments about the following points, as well:

- the thermal load profile is quite important to determine how to define the system response and the control solution behind!?

- In terms of an efficient approach, do we have to consider two clear heating modes, a stand-by mode and a second mode (a kind of booster) for during the mass periods?

- Dynamic heating load analysis? Simulation ?

May we listen the Forum.
Thank you!
Welch

 

[briand2]

Here is something to think about, from CIBSE in the UK:

"Thermal mass and controls
One technique often used to save fuel is intermittent
heating. This allows the building to cool down overnight
or when not occupied. The resulting lower average
temperature difference between inside and outside means
that, in theory, less fuel is needed.
This approach can create problems for masonry buildings
with high thermal mass, particularly if they are also damp.
As the building begins to warm up, surfaces, particularly
those most rapidly heated when the heating comes on,
begin to evaporate moisture at a high rate, raising the
dewpoint of the air. This may possibly even lead to
condensation on the cold structure at points which the
heat reaches more slowly. For example, in intermittently
heated churches with warm air systems, the floors
sometimes become damp shortly after the heating starts.
As this process is repeated, the effect is to distil moisture
from the warmer to the colder parts of the building. This
is most likely to affect windows, roofspaces, ‘cold bridges’,
window reveals, the corners of rooms, behind cupboards
and places where insulation stops. Mould growth - and
worse - can then ensue; and even glass can be affected
(see case study 18).
The second problem with intermittent heating is that, to
offset the ‘cold radiation’ from the unheated masonry
structure, the air has to be hotter than normal to provide
the same degree of comfort. The rapid changes in air
temperature and humidity can also cause damage to
decorated surfaces. There can be major problems where
salts are present, as these can re-crystallise as conditions
fluctuate. This can lead to accelerated deterioration of the
fabric and the rapid loss of historically and aesthetically
important surfaces such as stone carvings and wall
paintings.
Buildings with high thermal mass are generally better
heated continuously to a low level, or with night set back.
This can sometimes also prove more economical.
Occasionally, the use of a building is so low that full
heating cannot be justified. Here, one might consider
increasing the thermal comfort locally, for instance with
underfloor heating in the pew areas of a church. However,
in many buildings, a low level of background heating is
often justifiable as a form of preventive conservation, to
help keep the fabric dry and reduce the rate of
deterioration."

There are no right and wrong ways to achieve what you want, it's all a question of compromise...

Hopefully some others (with more experience of heating churches) will comment on this!!!

Regards,

Brian

 

[SAK9]

Radiant heating is suitable for places such as churches and indoor stadia as they are not in use most of the time.Further they have large ceiling heights required for radiant heating.Comfort is immediatly achieved with radiant heating as the heat reaches the occupant without the aid of a mediium.It is also not necssary to heat up the walls before comfort levels can be achieved.

 

[Welchita]

Thank you for these two interesting replies!

To Brian:

Can we learn more about the source you mention?

When you make the citation:

"Buildings with high thermal mass are generally better heated continuously to a low level, or with night set back. This can sometimes also prove more economical.": -

What temperature levels are thinking about? Above the wet-bulb temperature?

The humidity problem is what your citation mainly tells us about! When we enter in crowded church in the winter, we smell of something, that is part sweat and part humidity, as well.

However as you know, that wet-bulb temperature varies in function of the air humidity level and that changes quite a lot during and after a mass period.

It is logical that we should have some control on the interior air humidity levels in these periods and along after, should we?

To SAK9:

I agree with you.

But radiant heating means to have radiant heating surfaces distribuited all along the ceiling, or walls, and that means some implications for a built church.

Well, here we can try some compromise, but I think the solution will be something hybrid like radiant heating plus some control (not a very expensive one) on the interior air humidity levels, as said above.

The discuss is on. Please, let's hear more experts.
Welch

 

[briand2]

Welch,

CIBSE is the Chartered Institution Of Building Services Engineers, a UK organisation (

http://www.cibse.org).

They produce guidance on all aspects of building services, for all types of buildings. They are the UK's equivalent of ASHRAE.

There is no single right way to achieve what you want / need. In common with all buildings, churches have varied systems including underfloor heating, warm air heating, central heating to radiators, gas fired wall mounted heaters, radiant heaters, etc. Of these, gas fired wall mounted heaters are probably the most common (as seen at this link:

http://www.christiansuppliers.com/pages/listgen.asp?layout=description.asp&Author=GR-106-592).

Such rapid warm-up periods would be less desirable if the churches contain priceless works of art, but not all churches contain these.

In the UK, it is not usual to try to control church humidity other than by reasonable ventilation.

Here's a link to one approach (not UK) to this problem: "

http://www.ucl.ac.uk/sustainableheritage/conference-proceedings/pdf/2B.9_kozlowski.pdf".

Regards,

Brian

 

[friartuck]

Apart from surveying dozens of churches, I have designed a few church heating systems as well.

Not one of the easiest exercises.

First of all the 'old' churches are thermally heavy and consequently take a lot to warm them up.

Heat up times can be a few days on large churches, hence it is better to keep them at a 'set back' with boost to get the accepted space conditions.

There are lots of solutions, ie electric radiant, fan convectors, under seat heating, underfloor heating etc.

One problem we did encounter was the 'self learning optimiser'system. (For anyone outside the UK, an optimiser when applied to heating systems is a smart time clock.

This has the ability--(so we thought) to learn the buildings warm up times. The isea being that it can pre-emp the boiler start time or switch off the boilers before the schedules normal 'off' period.)

These systems work fine in 'normal' buildings. But when the building time constant is excessive (i.e. several hours or a few days ), thenm the programmer just couldn't cope.

In this instance, we opted for a simple manual control with a set back for the rest of the time.

When estimating heat required, the 'Y' value or admittance factor is a better indicator of the heating requirements rather tha a simple steady state 'U' factor.

A well insulated building would typically have a U value of 0.35w/m2C. A church with a thick stone wall however might have a U value of 1.0 or 2.0 but an admittance factor of 4 or 5.
In essence, the Y value is a measure of the heat flow INTO a fabric rather than through it.

CIBSE has Y factor tables and has a calculation method for asssessing them as well


Ciao

Friar Tuck of Sherwood

 

[Welchita]

Thank You your reply Friar Tuck. How is Robin Wood?

We think these contributions can now serve as platform to focus us in one or two ways to solve the problem. Please, let´s put some conclusions on the table.

In fact, how can we assure a comfort environment in a church with an heavy thermal mass, which is to be used for one or one and half hours/day, and during the weekends, 5 to 7 hours?

This church is an almost modern one and it doesn't have very sensitive art objects, well just a few. Anyway I’m going to analyze specifically this aspect.

One of our goals is to defined an whole energy efficient heating system, that means to heat where and when it is really needed.

A possible hybrid solution, could be to combine an heating floor system, (It has to be very isolated from the underground stuff)in the benches areas and corridors as well with radiant panels fixed on the lateral walls (I have to negotiate with the architect those implications) with circulating hot water (around 75 ~85 ºC, or 167 ~185 ºF).

In terms of control routine, we could apply an automatic stand-by mode to keep the heating floor system, the ground surface temperature above the 12 ~ 14 ºC or 54 ~ 57 ºC.
In warm-up periods, that temperature would be increased to 20 ~ 25 ºC or 68 ~77 ºF.

At the same time, the radiant system would be just turn on manually during the mass period, (as it was a light system), to serve the occupied zone.

May we have your comments? Thank you.
Welch

 

[briand2]

Friar Tuck,

Don't you find that using the Admittance (Y-value) for the heating is something of an overestimate? I totally agree that heating a church, even with an out-of-hours set-back temperature, is not steady state. However, I've only used admittance when carrying out summertime temperature calculations (as per CIBSE guide) in non-air-conditioned buildings, where admittance can be used to even out hour-by-hour loads. When a church is heated for Sunday, it's heated more or less all day (from Saturday evening, in some cases), so perhaps the true figure lies somewhere between U-value and Y-value?

I note that you have experience in designing for churches, whereas I've done design for more or less everything else apart from churches (but I've been too cold and / or too hot in plenty of them!!!!).

I think Welchita's hybrid solution seems all right, but my gut feeling is that it's perhaps a little sophisticated / expensive...?

Regards,

Brian

 

[friartuck]

I haven't found an ideal solution. The fact is, heavy weight churches are a pain to design heating for.

Though one solution did work fairly well.

We used fan convector heaters and destratification fans. The destrat fans were a special type which you may never have come across. The fans blow air upwards and not downwards. The idea being that cold air blowing up will gently displace the hot air at high level and bring it down to low level. (NuAire Ltd. System 200 if you want technical details)

The church was heated to a low level (Set back of around 14-15C). Boost was provided for a few hours prior to occupation with the desrtat fans running at high speed.

These were then turned to low on occupancy.

Briand 2. You are right, the Y factor is an over kill, but I would guess that over sizing on steady state Plus 50% wouldn't be unreasonable.

Ciao


PS Welchita...Its Robin Hood (Though He might have had a distant cousin called Wood)


Friar Tuck of Sherwood

 

[Welchita]

Hello SAK9!

To BRIAN:

My guess, the less expensive goes to consider only the radiant system, which has to be on, a while before the mass period just to warm-up the floor, walls and benches surfaces in order to reach a kind of surfaces radiant equilibrium, near of some comfort condition as well, based in what SAK9 has said to us before.

Hello SAK9, at this stage of the discussion would you like to comment, as well?
Thanks!
Welch

 

[SAK9]

The effectiveness of radiant heating system depends on how well the heaters are distributed in the space.I have used them for factories and warehouses with high ceilings.It was not a problem in those buildings to locate them throughout the space in a unifrom way as they were suspended from the ceiling.Things are different in a church especially if you have a large span.In such an event the wall mounted radiant panels may not serve the centre area well.Given such a scenario complementing your system with an underfloor heating system makes sense.

Since you have mentioned that this is an existing church,the costs for doing an underfloor heating system could go up significantly.

Please examine the possibility of having uniformly suspended radiant panels with the Architect though they may not look aethetically very pleasing.

Even with radiant heating you do need a warm up period to heat up the furniture ,carpets,wall skins etc

 

[Welchita]

Hello Folks!

It has been a very pleasant discussion so far, I think we got already a main solution to explore and apply to the the case, I'm dealing with. So, I thank You All for the very good contributions. Nevertheless, this doesn't mean the case is closed, on contrary....

Have a good week to All! Kind Regards.
welch

 

[RobWard]

Has anyone used this sort of longwave radiant heating?

http://www.energostrip.co.uk/

I ask as it is something we are considering for a new project but haven't come across anyone who's used it before, and it show it being used in a modern church.


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