Industrial buildings

[Paul Mallion]

Has anyone put an industrial building through PHPP? I am working on a large art studio which would be classed as light industrial use. The ceiling height is min 4m to suit large artworks.

The building therefore has a very large surface area in proportion to its floor area, making it very hard to achieve 15kWh/m2a. Even using opaque U values of less than 0.1 all round fails to make much difference to the specific heat demand. Occupancy and heat gains from processes are quite low in this case, and there are relatively few windows for solar gain, apart from some northlights.

TFA is 165m2, volume 768m3, specific heat demand is currently 25kWh/m2a. Advice on how to reduce further without improving U values to ridiculous levels would be welcome.

[Anonymous]

I'm a great fan of PHPP but perhaps this is a situation that exemplifies there are limits for all things. Northlight has been valued for centuries by artists and design craftsmen but doesn't score any points in PHPP! Equally, PHPP requires a warm, even temperature but many artists and craftsmen have little need for either.

I suspect it may be worthwhile in this case to look at 'massive insulation' and 'decrement delay'; I'm thinking of the Adnams and Wine Society warehouses, and the Sworders auction room as examples. As Nick says, you can use PHPP as a design tool without having to accept its verdict. And as Mike says, there are other tools in the box.

[Nick Grant]

Just to be clear Paul was asking about achieving the Passivhaus standard which is a deliberately non-negociable target (for new build at least) and can only be demonstrated with PHPP.

If you want to see how an unheated or sporadically heated building will perform in terms of temperature then sure you need a dynamic model.

Nick

[Anonymous]

Sorry Nick but I don't see the point in giving advice to anyone about software which cannot be used to demonstrate compliance. Far better to advise them of this fact I think so they can move on to something which will do the job.

The fact is that all commercial buildings require either the use of SBEM [simply shaped buildings] or Dynamic Simulation [more complex buildings] Paul will also need to use one of the above to produce an EPC.

Both of these requirements are set out in Part L2A

Dynamic software will of course give results in units concurrent with the PH non-negotiable target method

[Mark Siddall]

I don't see a reason why the PH standard can not be achieved. There are PH schools, offices, fire stations and industrial buildings.

Questions:
1) To achieve the 15 kWh/m2.yr have you optimised the design for passive solar? Doesn't sound like it – this will most certainly be making life harder
2) You can satisfy the PH standard by satisfying a peak load of 10W/m2 (though this will require suitable weather data to assist with determining peak load.) Using the Manchester weather data what's your peak load?
3) If you can not optimise the design to satisfy either of the above
4) If all else fails dynamic analysis may be useful for demonstrating compliance with PH standard.

Cheers,
Mark

[Nick Grant]

Mark

I didn't think it is possible to demonstrate PH compliance (ie for certification) with dynamic simulation. I know PHPP is based on dynamic models but the issue is the simple level playing field to demonstrate compliance.

Paul is right that it will be a struggle as this building is relatively small but with high roof, whatever model is used the physics remains the same, area looses heat.

One of the beauties with PHPP is it can be used quick and dirty and I just modelled your building assuming it is square in plan. By tweaking windows and insulation I get between 20 and 30kWh/(m2.a) (very crude, I have no idea what this building looks like but assumed a good chunk of high level North glazing).

However as Mark suggests it looks quite easy to hit the 10W/m2 heat load target which is an alternative route to compliance (based on Manchester data).

I really should be working but was curious and it only took 5 minutes.

Mike, Paul was not asking about scraping through Building Regs and it is a pain that we have to double up in order to get an EPC. Perhaps this will change and Passivhaus Certification will be accepted as evidence of compliance. I do think it is worth remembering that PHPP was developed by physicists wanting to close the gap between models and reality that continues to plague eco buildings.

Unless I misread your post, you seem to be suggesting that Passivhaus is a dead end approach??

Paul, interested to hear how you go with this.

Cheers

Nick

[Anonymous]

4) If all else fails dynamic analysis may be useful for demonstrating compliance with PH standard.

Cheers,
Mark

Why do you say only 'may' Mark? What does PHPP do that Dynamic software cannot?

[Nick Grant]

Mike

I think the real value lies in what PHPP stops you doing! The big danger with any model is that we begin to believe that they reflect reality when in fact they just manipulate our assumptions.

[Anonymous]

I get between 20 and 30kWh/(m2.a) (very crude, I have no idea what this building looks like but assumed a good chunk of high level North glazing).

However as Mark suggests it looks quite easy to hit the 10W/m2 heat load target

That worries me. I'd assumed that the 15 kWh/m2 and 10 W/m2 were roughly comparable metrics and that's why they were now both allowed. But the fundamental metric must be the total energy consumption – the 15 kWh/m2 – and it's worrying if you can get away with twice the energy consumption by using the alternate metric. Or did I miss something?

Cheers, Dave

[Mark Siddall]

Nick,
As I understand it dynamic modeling can be used to compliment PHPP – though mainly with thermal mass. I'm not suggesting that dynamic is an alternative. In this case – studios – I was thinking that some form of zoning may be appropriate. (Though I would like encourage greater use of passive solar I have to say that for a pure 'compliance' the lead approach I think that the 10W/m2 option is likely to stand a better chance of success in this particular instance.)

Dave,
Due to the influence of passive solar the 15 kWh/m2.yr is not directly related to 10W/m2. In smaller UK homes (~70sqm) the 15kWh/m2.yr can be achieved by providing more south glazing. The consequence is then that the 10W/m2 can not readily be satisfied without an excess of insulation. In slightly larger buildings it may be easier to satisfy both criteria and larger still just the 10W/m2. From my having examined terraced homes in PHPP 10W/m2 could result in about 22 kW/m2.yr if passive solar is not optimised. Personally I don't find this particularly worrying or surprising but I think that it does offer a useful sense of perspective.

Mark

[Nick Grant]

Mark
Good question for next week but my understanding is that it is recommended for thermal comfort check in buildings with high gain and mass rather than as an alternative route to compliance with the energy targets. Problem with using it for the latter might be how to check all the assumptions? From my 5 minute dabble I think you are spot on about the annual heat v energy demand for this building, Paul, go for <10W/m2.

Dave
Nothing to add to Mark's points and there is some discussion of this elsewhere. My take on this is that the calculations are not a prediction of actual energy use, which depends on all sorts of variables such as people, but a prediction of whether the building fabric and ventilation has been optimised. In this example the form has to be sub optimal (if it was a house an extra floor could be added by raising the roof a little and this halves the kWh/m2 by doubling the floor area). So 10W might be a good target to aim for whilst 15kWh/m2 becomes an expensive goal.

Mike
Whilst I'm always up for a good argument I think I will resist and let someone else explain the similarities and differences between PHPP and rdSAP.

[Anonymous]

Mike
Whilst I'm always up for a good argument I think I will resist and let someone else explain the similarities and differences between PHPP and rdSAP.

LOL Nick, I think I know the differences between PHPP and rdSAP. That wasn't my point- but I think you know that.

Not looking for an argument anyway but I did ask what I thought to be reasonable questions [haven't had an answer sadly]

1. What does PHPP do that Dynamic software cannot?
2.What difference does it make whether a building is labelled Pasivhaus or not?

[Nick Grant]

As you insist Mike

I made the quip about rdSAP as you suggested that was the logical conclusion for my line of reasoning. My point is that PHPP evolved as a solution to plugging the gap between design and reality for low energy buildings. Clearly the laws of physics were not to blame and the power of PHPP is that the assumptions have been well thought through and tested over many years and can hardly be called 'reduced' hence my quip. If I was working with a perfect energy model there is no way I'd think to allow for the heat loss due to towels drying or plants transpiring and I wouldn't have realised how significant some thermal bridges are or duct insulation, or your favourite, heat loss to ground.

These assumptions are for all to see and are being continually refined (I assume you have watched the You tube discussion between Pete Warm and Wolfgang Feist on internal gains).

What the physicists working on PHPP found was that a simplified steady state model gives very good results compared with dynamic models (which they use every day for research) because a comfortable low energy building is pretty much steady state. Even the monthly and annual methods yield very similar results for most building designs.

What makes the real difference is not whether heat flow is calculated on an hourly or annual basis but on whether your assume 2W/m2 or 8W/m2 net average internal heat gains or whether you fully consider thermal bridges due to window installation.

So yes, you win, a dynamic thermal model does so much more than a simple spread sheet and is so much more accurate. That is why they are used to model cutting edge environmental projects such as Portcullis House (was it 4 or 5 times the predicted energy consumption?) and Swiss Re or any number of eco schools etc etc.

Hopefully that answers 1.

2. The label is crucial. We have been building, 'eco', 'low energy', zero carbon etc buildings since the 70s but what does it really mean? Can you complain that the house you commissioned was not truly eco? How high do the fuel bills have to be?

Despite being deliberately unprotected as a trade mark, to call a building a Passivhaus is a very clear claim that can be verified. Sure the actual energy use may be more of less but it must be airtight (<0.6 a/c @50Pa), thermal bridge free (<0.01 using external measurements) and have calculated energy OR heat load of 15 kWh/(m2.a) or 10 W/m2 according to PHPP.

Other climate specific measures such as minimum window U values (0.85 installed for UK and Germany) etc are based on clear comfort criteria.

I think we have scared Paul off. Let's just agree to disagree.

Nick

[Paul Mallion]

Thanks for all your comments and suggestions. In this instance Canterbury City Council wanted to place a planning condition that we obtain a BREEAM Good rating, I managed to persuade them that achieving PH, or as close as practicable, would be better. They have agreed and client would like to get certification if possible, but not essential. SBEM will be used just for EPC purposes.

Being an artists studio, passive solar is not possible, the constantly changing pattern of sunlight is not acceptable (we are talking serious professional artist here). The site is shaded on the south at low level anyhow, being on a slope and close to hedging.

The building form is a simple rectangle, with glazing concentrated at the west end, well shaded, and northlights. Recent changes in glazing/rooflights and adding certain cold bridging has changed Heat Demand to 30, with Heating Load being 15. I have some more work to do on inputting the working patterns, lighting loads, occupancy levels etc, but it seems that all these refinements do little to Heat Demand. Adding 50m2 of floor area (mezzanine floor) brings it well within target, but is not what we want to do. Actual heat demand would not be greater if we did add a mezzanine, occupancy would be the same. The problem with all software is that you eventually find ways to fool it and do what you want.

This is partly the argument that has raged in the last few days, do you use the software as gospel, or as a guide? As Nick points out, PHPP has been post tested time and time again to prove that it is within a range of accuracy, unlike SAP. I am not aware of post occupancy testing that may have been done on dynamic software, but I am not going down this route anyhow.

I will certainly look at achieving 10W heating load as this seems within reach, thanks for that advice. If we go down the certification route, who would you recommend to certify? Passiefhuis Platform have quoted 600 Euros, BRE in region of £3000 plus £600-700 for each psi (ouch), Peter Warm is not qualified yet, I believe. Will post plans if interested.

Paul

[Anonymous]

Paul, here's an off the wall idea. I'm a shutter nut – have you thought about insulated shutters to cover the rooflights at night? What happens to the heat demand/load if the rooflights have unfeasibly better U-values with an unchanged g-value?

Perhaps more mainstream, is there any scope to replace windows and/or rooflights with translucent panels such as Kalwall Nanogel? It would improve the U-value but also knock the g-value so the trade off may not be worthwhile.

Cheers, Dave

[Anonymous]

Mark, Nick, Thanks for the explanation about kWh/m2 vs W/m2. It helps some but I still have a concern. I appreciate that the actual energy usage may vary but these numbers are still the best estimates. My concern is that the two numbers address different goals, as far as I understand.

I think the 10 W/m2 limit is concerned with making it possible to heat the building using the ventilation air, so it's important to know whether it will be achieved or else to make provision for some additional heat distribution. So it's a technical number that affects the design and costs.

The 15 kWh/m2 limit is concerned with the total energy used by the building and is a [not especially accurate] proxy for carbon emissions. So it's a much more strategically important goal in my mind. In theory a building could meet the 10 W/m2 limit and still use 87.6 kWh/m2, which would not be good.

[Anonymous]

Thanks for the answers Nick.

So to clarify.

1. What does PHPP do that DSM cannot?
Answer- nothing

2.What difference does it make whether a building is labelled Pasivhaus or not?
Answer – is an opinion. I respect yours but will agree to disagree as you so politely suggest.

[Author]

Posts