ASHP to heat warehouse with internal offices - is this the best way? Plus Solar PV?

[Sven7]

Hi All,

 

I hope someone sensible can help point me in the right direction or offer some useful comments on our project...! 

 

We'd initially planned to heat the whole place using an oil fired boiler with a wet system - underfloor tray system for the office space with warm air blower to keep frost off the warehouse space in the winter. But now we're wondering whether we can heat the office area appropriately with an ASHP throughout the year, possibly supported with PV panels on the roof? (It's a large roof, approx 250sqm is south facing, unobstructed - we can trim the trees). 

 

 

Outline as follows:

 

We have a steel portal frame barn which we're converting into a warehouse with internal offices. The existing asbestos roof and steel sides will be replaced with insulated Kingspan panels (KS1000RW 100mm for roof and 73mm for the sides - both with U Value of 0.18 W/m2). The building measures 25m x 17.5m, average height is 5.25m. (see plans)

 

Within the building is the office, which measures 8.3m x 15m x 2.6m.

 

Ignore the additional small building on west side it's being demolished.

 

When it's -3 deg C outside we'll need to maintain approx 10 deg C in the warehouse and 22 deg C in the offices. The place is only occupied during normal office hours. i.e. I'm not worried about keeping it warm at night, just that it doesn't freeze!

 

We guess our heat demand would be approx 4kW for the office area and 16kW for the warehouse. (Maybe someone can tell me if this is miles off?).

 

How can I work out how much energy an appropriately sized ASHP will USE across the year? 

 

Furthermore, we've got a great big roof area relative to the size of the office to be heated so can Solar be used to power the ASHP for most of the year? I guess in depths of winter when it's grey and wet the contribution would be minimal... at the time when the ASHP will be doing the most work and COP would be at its worst? What would a sensible output of PV be?

 

Any advice warmly welcomed! 

 

Many thanks,

Sven

 

 

 

 

Proposed.pdf Floorplan.pdf birds eye.pdf

Edited November 1 by Sven7

[sharpener]

If you are going to re-roof the buildiing you should max out on the PV generation in any event, it will pay for itself in short order. You can estimate the output using PVGIS.

 

As for heating with an ASHP (or several) you should start with an estimate of heat loss, you can DIY by downloading the free sw from heatpunk. This is primarily designed for domestic buildings but should give you an idea. You can model the offices as a separate building with an ambient of 10C to begin with.

 

Capital cost likely to be higher than oil-fired, running costs maybe somewhat lower esp. as your target temp is modest so CoP should be high.

 

Sounds like you need a local firm who are into heating commercial buildings in a serious way, has yr architect/surveyor not got any suggestions/contacts? If you say whereabouts it is someone on here may have a recommendation too.

 

 

[Russell griffiths]

My view based on a friend who owns a fair few buildings like yours that he rents out. 
 

offices, you can build these to a very high standard inside the main building envelope, so easy to heat. 
I would fit air conditioning units in here so you can cool in the summer and heat in the winter. 
fit Solar to offset the cost of running the air conditioner in the summer. 
 

the warehouse space is a different ball game, forget the u values of those sheets, unless you build this meticulously it will still be a draughty warehouse, you will struggle to get any form of sensible amount of heat in it without it escaping out of every roller door, or roof to wall junction, the floor is one huge cold spot sucking any warmth from the building. 
 

either an oil or gas hot air blower system is the only thing I know that will heat that amount of volume. 
 

or a big biomass boiler and thermal store. 

[saveasteading]

1 hour ago, Sven7 said:

When it's -3 deg C outside we'll need to maintain approx 10 deg C in the warehouse and 22 deg C in the offices.

I am assuming GB conditions.

 

You heat the office with ashp, and remember to insulate the walls to the warehouse, and the ceiling.

A lobby at the outside door will keep the heat in.

 

The warehouse doesn't need heating.  It would be hideously expensive to do so, and it would end up hot in the roof and cooler at the floor.

Heat loses through open loading doors are extreme, of course. Through a closed loading door there are still draughts especially at the spring unless you go for top of the range.

 

If your concern is for the product , then install a primitive gas or oil heater linked to  a thermostat. It may only fire a couple of times a year.

 

More importantly, keep the door shut.

 

You say it is a barn. I hope you know that an agricultural barn is designed without factors of safety and needs reinforcing for other uses.

 

1 hour ago, Sven7 said:

hope someone sensible can help point me in the right direction

 

You have come to the right place.

 

[SteamyTea]

Definitely A2AHPs for the offices.

 

Generally warehouses don't need much heating, their form factor works in their favour.

Much will depend on how the area is used. There is a difference in constant temperature or intermittent temperature when it comes to system design.

@saveasteading has some experience of refrigerated storage, same physics applies to warming a place.

PV is worth fitting as you can sell excess generation i.e. weekends.

The main thing to check first is how much power your DNO will allow you to connect up, they may also have something to say about very large heat pumps starting up (rightly or wrongly). Check that first.

 

Forget biomass.

[SteamyTea]

See @saveasteading nipped in before I posted.

[saveasteading]

28 minutes ago, SteamyTea said:

their form factor works in their favour.

A good point. Very little heat disappears down through the floor of  a big shed, as the outdoor effect diminishes away from the perimeter.

This is understated by the insulation manufacturers.

Thus you are even getting some warming from the ground if the internal temperature happens to plummet.

 

Just a thought....I was told that B and Q warm their stores with gas or oil heating , but with the exhaust also sent  indoors.  This is on the basis that they are only taking the edge off the cold, and the volume is huge.  I'd be interested if someone more expert can confirm or refute this principle.

 

If you have work stations within the warehouse it is simple to install local radiant heating. This will then spread around the space and may provide the extra degree that helps through the February night.

 

And I haven't mentioned airtightness. You have the benefit of these trees against the wind, but draughts will suck out your nice tempered air. The worst leaks are often  at the interfaces of the walls to the roof and slab.

[SteamyTea]

1 hour ago, saveasteading said:

I was told that B and Q warm their stores with gas or oil heating , but with the exhaust also sent  indoors.

I doubt that, they may have some kind of heat recovery on the exhaust, but that is what condensing boilers are doing already.

 

I keep meaning to measure the heat load at work, must have a word with the site manager.  Would be interesting as we use resistance heating, and even when I go in early, it is never very cold.

[Roger440]

Hmmm, this is interesting. I too have a 3000sqft "warehouse" that is my workshop with some accomadation built in.

 

The accomadation is insulated all round with 50mm PIR so not great, but OK.

 

I want to keep the main area at 12c over winter. But without it costing a fortune.

 

Ive spent ages going over all sorts of options, for insulation and heating, so far with no decision. The accomadation is currentl;y direct resistance heating which is bankruptcy inducing to use.

 

All this talk of draughts is valid for your regular commercial building, but can be overcome with good attention to detail with the insulation.

 

Its interesting that, almost universally in the UK, warehouses are unheated, with local radiant heat for operatives at packing stations etc.

 

However, our owning company in Poland, their warehouses are all heated to 16c. Unsurprisingly, they are all heavily insulated. Pretty normal there. Ive also visted sevaral in germany, including a couple of huge ones. All heated. It can be done.

 

[saveasteading]

4 hours ago, Roger440 said:

All heated. It can be done.

Of course it can be done. But is it necessary? Forklift drivers can wear warm clothes indoors as they can outdoors.

For perishable goods I think I'd be more concerned about summer heat. Up at the roof space it can get horribly hot, and the plan shows skylights.

[Mike]

5 hours ago, Roger440 said:

All heated. It can be done.

It would have to be done, as would @Sven7's. When heating a warehouse by more than 2-3 °C or so (the minimum necessary to avoid frost), then the entire building would need a thermal upgrade to meet the requirements of Building Regulations, unless it's already insulated to the required standard. Though the standard is no doubt still lower than Poland / Germany would require. I imagine the same would apply to summer cooling, though I'm less familiar with the non-domestic Regs these days.

 

If heating is limited to frost-protection in the warehouse section, then only the offices would need to be insulated.

 

Edited November 2 by Mike

[Roger440]

9 hours ago, saveasteading said:

Of course it can be done. But is it necessary? Forklift drivers can wear warm clothes indoors as they can outdoors.

For perishable goods I think I'd be more concerned about summer heat. Up at the roof space it can get horribly hot, and the plan shows skylights.

 

Circulation fans will be essential, and useful whatever else might be done.

[saveasteading]

3 minutes ago, Roger440 said:

essential

I'd say no, its an option. Very seldom used.

We don't know much about the location or product so can't get so precise. 

And the OP  isn't responding so I'm ducking out.

[Roger440]

8 hours ago, Mike said:

It would have to be done, as would @Sven7's. When heating a warehouse by more than 2-3 °C or so (the minimum necessary to avoid frost), then the entire building would need a thermal upgrade to meet the requirements of Building Regulations, unless it's already insulated to the required standard. Though the standard is no doubt still lower than Poland / Germany would require. I imagine the same would apply to summer cooling, though I'm less familiar with the non-domestic Regs these days.

 

If heating is limited to frost-protection in the warehouse section, then only the offices would need to be insulated.

 

 

Yes, sadly the whole building regs issue comes up. Given the proposed insulation by the OP, im guessing thats the requirements for a commercial building as it clearly is less than domestic.

 

I wont comply as to do so would be prohibitively expensive. The roof for mine, just the roof, came in at circa £50k. Id have to live until im 300 years old to see any payback. As always, the requirements put you in an "all or nothing" situation. 

[Roger440]

1 minute ago, saveasteading said:

I'd say no, its an option. Very seldom used.

We don't know much about the location or product so can't get so precise. 

And the OP  isn't responding so I'm ducking out.

 

In mine, with its completely uninsulated roof, its always noticeable warmer up near the roof. Pushing that air back down is almost free.

 

Yes, OP seems to have disappeared? Shame as it looked interesting.

[saveasteading]

1 hour ago, Roger440 said:

sadly the whole building regs issue comes up

It is an unheated building so doesn't need insulation, although it is prudent to have some.

The office is secondary and can be dealt with on its own merits.

1 hour ago, Roger440 said:

In mine, with its completely uninsulated roof,

How cold does it get relative to outside?

[Mike]

5 hours ago, Roger440 said:

I wont comply as to do so would be prohibitively expensive.

That's not such a trivial decision now that there's a 10-year enforcement period (plus the possibility of an unlimited fine and/or up to 2 years imprisonment - though presumably much less for that for an insulation offence).

[Roger440]

9 hours ago, saveasteading said:

It is an unheated building so doesn't need insulation, although it is prudent to have some.

The office is secondary and can be dealt with on its own merits.

How cold does it get relative to outside?

 

With a sustained cold period very! Same as outside pretty much

 

Walls are block cavity, so that slows things down, but is just cement board roof.

 

Ive got waste oil burner with blower that i now run on red diesel, but that makes for expensive warnth!

[Roger440]

6 hours ago, Mike said:

That's not such a trivial decision now that there's a 10-year enforcement period (plus the possibility of an unlimited fine and/or up to 2 years imprisonment - though presumably much less for that for an insulation offence).

 

Yes, i mentioned that in my other thread about my house, which is why ive considered involving a BCO, where, normally i wouldnt. 2 years inside for fitting a window seems like overkill V the offence. How dare i. I should allow someone with a can of squirty foam, but sporting a fensa certificate to do a crap job instead. 

 

For my barn/shed call it what you will, trying to comply means costs approaching 100k. Its just a (big) workshop for my cars, toys and stuff. Not happening. I can of course make it much better for circa 20k, but that wouldnt be allowed. Even at £20k, its cheaper just to burn diesel. Id just prefer it stayed warmish at a more constant level, as it will be better for the stuff in there, and means it wont be freezing cold when i go in there in the morning. Takes a coule of hours for the blower to get it from zero to 12c.

 

 

 

 

[SteamyTea]

8 minutes ago, Roger440 said:

Even at £20k, its cheaper just to burn diesel

As you have an uninsulated roof, why not create a large solar thermal collector from it.

Really just a case of a gap below it, then some insulation.  Blow air though the gap when the sun is shining.

If you want to get really cleaver, then pipe some of the warmed air though a tub of stone chippings to store the energy for later.

[Roger440]

1 minute ago, SteamyTea said:

As you have an uninsulated roof, why not create a large solar thermal collector from it.

Really just a case of a gap below it, then some insulation.  Blow air though the gap when the sun is shining.

If you want to get really cleaver, then pipe some of the warmed air though a tub of stone chippings to store the energy for later.

 

Indeed, you have suggested this previously. I like the idea, though at a practical level there are some challenges, mainly the purlins that run along the roof blocking said airflow. And the roof is heavily shaded after midday/ early afternoon by 30m conifers.

 

But ive not abandoned the idea. I did originally start a thread on how to heat the place at zero or close to zero cost.