Tas, IES or Hot3000

[Tom Foster]

Which is best, pros and cons?

(At risk of duplication http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5193 but wishing to consult both forums)

[Mark Siddall]

PHPP 😉

[Nick Grant]

You wind up merchant Mark!

I have to agree though.

Alan and I have been working alongside various engineers who are using TAS and IES. The results vary hugely but not because of the 'engine'. Is all down to assumptions. It should be possible to get IES and TAS to produce better results with more realistic internal gains and suitable fudges for thermal bridges but life is too short. PHPP allows instant what if scenarios that would take hours in IES.

Don't be fooled into thinking that models that use minute by minute temp and radiation data will necessarily be more accurate than a simple degree day model. Even anual and monthly models give quite similar results.

PHPP will be demonstrated on the AECB stand at EcoBuild (times to be agreed) so if someone wants to turn up with IES on a laptop we can show and tell.

Nick

[Anonymous]

Is this because PHP already has the assumption built in so you do not need to think about them? IES/TAS have a much wider scope of application than PHPP and therefore the options available are much greater and more flexible. IES/TAS are in a different league to PHPP – PHPP is a much more specfic product, orientated towards a particular level. Are you not assuming that the IES/TAS results are wrong because they are not the same as the PHPP?

[Nick Grant]

Nathan you are right, I was being simplistic.

PHPP assumes a low energy building operated at a constant average temperature and does not attempt to model over-glazed buildings with high levels of thermal mass. That is 100% of the new build projects that I am likely to work on so PHPP suits me fine.

I am not saying the IES results were wrong in terms of maths, only that it seems common for users to assume higher internal gains when calculating heat requirements and this results in conclusions such as the building has no heat requirement so less need for insulation or HRV. I think this is probably the main explanation for the huge gulf between design and reality that is the norm for many so-called low energy buildings.

PHI have put a lot of effort into determining realistic net internal heat gains and you will have seen the video interview between Pete Warm and Wolfgang Feist discussing this. For design reasons you can calculate IHGs in PHPP but for certification you have to use the defaults where they exist to prevent cheating (zero heat building heated by electrical goods).

The writers of PHPP use dynamic models and would be bemused by a discussion as to which is best.

I can see a dynamic model having an edge for very glazed high thermal mass designs but then I have not seen such a design that actually works and is comfortable so I'd rather play it safe and stick with what I am confident with. This means reducing the heat flux (in or out) to a level where the modelling can be quite simple.

I would also see a role for dynamic models in checking summer overheating in larger non-domestic buildings.

Or have I missed something?

Nick

[Mark Siddall]

Hi Nathan,
I've heard that some dynamic tools don't allow for psi-values to be enters (you have to enter Y-value instead – which a a bit sloppy in a low energy building.) Can you enter psi-values in IES?

Mark

[Nick Grant]

Nathan

In PHPP you would not worry about modelling temperature stratification as that is dealt with by the design philosophy which addresses radiant temperature asymmetry and glazing temperatures that could lead to downdrafts etc.

In terms of modelling what happens if you leave the building unventilated in summer on a specific day with a specific user behaviour – well no PHPP doesn't do that. What it does do is say the building will overheat if the ventilation (day and night separate) is insufficient WRT the gains and mass. It's a crude tool calibrated by dynamic models but it seems to work in practice.

If you are going to EcoBuild it would be interesting to meet up on the AECB stand and perhaps run a comparison. If you have an hour free we could model a simple building and try different window frames, glazing, insulation, shading, orientation, ventilation etc and see the effect on energy demand and summer overheating.

Nick

[Tom Foster]

V gd discussion of PHPP vs 'universal' modellers. I've no doubt that PH is a miracle of well-developed pragmatic usefulness, within its limits and assumptions, which are at present the best-practice mainstream – glad to leave that to the experienced wisdom of our PH specialists. I'm v interested in exploring what lies beyond PH – because believe me PH is only one step along the way, not the end of time.

Therefore, leaving PHPP aside, Tas, IES or Hot3000 – which is best, pros and cons?

[Mark Siddall]

Tom,
I must confess that I don't understand your premis of “beyond PassivHaus.” Once you've tackled the fabric and ventilation (as far as PH) then you're are left to concentrate upon DHW and electrical efficeincy – these are the most cost effective next step. At this point in time this is beyond even dynamic modellingsta as little is truly understood about behaviour (if it ever can be). Reducing the internal elec loads is obviously a big step, and this is considered when internal gains and the primary energy use.

Mark

[Nick Grant]

Tom

we jumped straight into banter but worth stepping back and saying what you want to use the software to help you model.

Nick

[Mark Siddall]

Good point

[Anonymous]

Sorry late replies…

Mark – no you can not put in the thermal bridges very accurately, in fact the u-value calculator is not brilliant either and this is one of the bad points of IES. In terms of the level of detail you currently look at in relation to bridges and junctions, the model is a little bit more basic. To accomodate you would have to adjust u-values to take into account thermal bridges. For residential I use another program which links the geometery from IES into a SAP program which has a better U-value. Thermal bridges can be entered on that but this is a manual entery.

Nick – I think this touches a little bit on Marks point. The level of detail in the thermal modelling does not match the level of detail in relation to PHPP. For instance, although shading, orientation, ventilation, glazing etc can be modelled, different frames become difficult. For instance, when looking at solar control glazing, I have to look up the glazed units on Pilkington to obtain the various short/long/shading coefficents etc and then adjust the parameters of the glazed unit within the model to get the same details. However I am guessing that if a material is not in the PHPP database you would need the details to enter in a a user defined material anyway. Coming back to frames, there is a selection for frame types however you are better off looking at the manufacturers window unit data and entering that data into the materail database rather than trying to “custom build” the unit within the software.

I am working on a project at the moment with an AECB architect who has already put the buildings through the PHPP software, so hopefully I will have the opportunity to compare. Alternatively if anyone has a small simple project they want to compare then please let us know – I think it is useful to compare a “real life” project.

[Anonymous]

Does HOT3000 have UK support or energy files for UK locations? I do not have an experience of HOT3000 but looking online it seems to be based on the Canadian market.
IES/TAS are both supported in the UK and have weather files for various locations through the UK, as well as around the world. I have had very limited indirect experience of TAS, however speaking to someone who has used TAS for decades(!) and used to work on mainframes(!) with the software, they advised that it was more to do with user interface than the actual software.

[Mark Siddall]

Hi Nathan,
Thanks for clarifying the thermal bridging issue. This worries me a little though. In a PH failing to account for the thermal bridging could suggest the building performs twice (or more) as well as it would in PHPP. Similarly with glazing, and the shading factor from the frames, this can have a major impact.

I appreciate that you could introduce fudge factors: One technique that I've heard about is to create a section of wall (1m wide/deep by X meters long.) You can than create a limited area of wall with an adjusted U-value (similar to what you suggest but localised to the detail in question rather than developing a whole building Y-value. But fudging the performance of the glazed area is far more problematic, esp if you can not readily tweak the frame dims.

Two more window related queries: In what detail can IES model windows? You suggest that window frames can be done, though it is demanding of effort. I assume that you can model all the mullions and transomes so that you can reflect the elevation (shading/reduced gains and additional heat loss). What about spacer bars? Can it manage the thermal bridging from these? Also is IES subtle enought to handle the shading from window reveals and window heads?

And one on DHW: Can you model the losses from the pipework to the internal environment? (Impacts upon primary energy use).

It'll be very interesting to see how you IES model compares to your architects PHPP calcs.

Cheers,
Mark

[Anonymous]

Yes i agree thermal bridging is a big issue – I have found on low energy homes the thermal bridging value has a bigger impact than the air permeability value. IES can account for thermal bridging but it does not calculate it (in the same way that SAP accounts for it but does not calculate it).

With regards to windows – there are different ways of putting in the glazing depending upon the level of accuracy. The frame can either be entered as a seperate material, or as a percentage of the window unit. Again with the elevation, you can literally draw the window unit as the elevation detail including spacer bars etc. This would take some time for this level of detail. Usually I model the fixed panes and the openeable panes. You can model that the spacer bar or frame is a different material, but this is not a 2D calculation. Shading from window heads and reveals can be handled; you can calculate shading from external roof overhangs, external and internal window shelfs, blinds etc – you can profile the blinds so that they are operated on a radiance level or other factors etc.

I do not have the pipework module for the system but know from previous similar software that the pipework design packages usually calculate the heat loss from the pipework based upon the insulation levels (this is needed to calculate the hot water return circulation flow rate when being installed).

I think the PHPP is probably very good but is very specialised towards a certain build quality/type. If you come away from the pre-defined standards set in PHPP then it may not be so useful i.e. this is a tool for designing a PH building. Where DTMS becomes useful is that it is suitable for all buildings – which makes it very flexible, but also very time consuming to get to the level of detail covered in some ways by PHPP.

I believe that IES was originally written and run in a spreadhseet.. maybe there is hope for PHPP yet…..

[Anonymous]

Mark

Looking through the forums came across this question from yourself.

https://aecb.net/forum/index.php?topic=716.0

This is something that can be modelled accurately in IES/TAS using actual external temperatures against internal temperatures rather than just assuming a set external and internal temperature for the MHVR to operate against. You would be able to output the results to determine the likely internal temperatures, and rather than just determine the peak temperature, you will be able to see the the frequency that occurs – important to ascertain the likley risk level of a stragety and ensures you do not install large expensive cooling plant just to cope with a one off peak.

This is were IES/TAS and other DTMS come into their own in their level of flexiiblity and “what if” scenarios.

[Mark Siddall]

Nathan,
In domestic build PHPP is accurate enough to assess over heating but for non-domestic buildings, as I understand it, PHI do encourage the use of dynamic models to assess over heating risk (thermal mass has greater relevance in such buildings).

Mark

[Nick Grant]

And the internal gains can be more peaky in time and location (eg kids in class). Main issue is PHPP averages out over whole building which is normally fine in a sensibly designed mechanically ventilated super-insulated building. However even the odd concentration such as a small server room can be calculated by hand if the loads allow cooling by ventilation. I would think that uncertainties about future kit would far outweigh any accuracies to be had from minute by minute thermal calculations.

[Tom Foster]

Tom,
I must confess that I don't understand your premis of “beyond PassivHaus.” Once you've tackled the fabric and ventilation (as far as PH) then you're are left to concentrate upon DHW and electrical efficeincy – these are the most cost effective next step.

As I say, PH is brilliant at what it does, but it's not the end of the road – there's always a 'beyond'! So I hope our PH experts, or even AECB with its sponsorship of Gold Standard etc, don't get left behind.

There is definitely more to concentrate on, than DHW and electrical efficiency, once you've tackled fabric and ventilation – especially as DHW and electrical efficiency, by reducing one kind of useful heat input (rightly, because uncontrolled and often electric) merely increase the requirement for fuelled backup heating.

What PH doesn't majorly address, is maximised solar capture as an alternative to
a) fuelled backup and
b) minimised heat loss.

PH is above all about minimised heat loss, as the key to everything, but that's a hard master to follow to the necessary limit (some say too hard for sloppy/cost-minimising British builders and bolshy British end-users) – and PH doesn't recognise that there's a more relaxed alternative. That is, to have more/maximised stored solar heat available, so that both
a) less or no fuelled backup is needed and
b) heat loss needn't be so rigorously minimised.

Solar, I'm guessing, came into evolving PH, first as an overheating problem to be screened out or safely absorbed. Then, I'm guessing, its limited usefulness as a heat source was recognised and that careful balance between overheating and usefulness became well developed. However the danger of overheating puts a low limit on the amount of solar heat that it's prudent to allow in. There's far more out there waiting to be harvested!

That's because PH can hardly conceive of any kind solar capture (leaving aside PVs and wet DHW panels) other than through window glass, incl sunspaces. And once inside the glassline, PH can hardly conceive of any way of receiving the solar heat, other than onto heavy surfaces. That form of receiving has severe limitations
a) as to quantity (intensity x glass area x duration) of solar heat receivable
b) as to ability to remain cool and so resist overheating, and
c) as to duration of storage of that heat.

The fundamental problem is that solar heat is received onto/into the massive heat-storage media on the same face as it later usefully comes back out. In that situation, it's roughly true that only the inboard 100mm of the massive element plays an active role, however deep and dense the element extends backward from its active in/out surface. That thickness of any mass can only offer 1.5 to 2 days max storage of heat, however deep and dense it is. That's the fundamental limitation of PH – solar heat storage duration insufficient to bridge over the length of typical sunless spells, during the heating season. No amount of heat loss reduction can compensate for that – after 1.5 to 2 days there will be nothing to supply the inevitable nett loss, however small that is, but fuelled backup heating.

How about if the building fabric were able to
a) receive and store far more (intensity x glass area x duration)solar heat
b) take it away (largely passively) to storage, from the receiving surface, as it arrives, so the surface remains cool and so does not overheat the interior, and
c) the duration of the massive storage is more like 10 days than 1.5 to 2 days?

Hint – the key to the above is storing the received solar heat into the back (remote) face of the massive storage medium, so that heat travels from there unidirectionally to emerge usefully from the front (room) face. That way, full benefit is obtained from all the density and full thickness/depth of the storage medium, rather than just from the inboard 100mm of it, as happens when the stored heat flow is bidirectional, in/out from the same inboard face.

Would that be a useful step beyond PH?

I look forward to hearing the flaws in this vision, to which I have a client willing to put his money where my mouth is and finance thermal simulation, to get the numbers/sizes on the principle, in this particular location. That's why I'm asking Tas, IES or Hot3000 – which is best?

Wish me luck!

[Nick Grant]

Tom

This was tried in the 70s and 80s. PH evolved as a solution to this failed experiment.

If you know of an example in UK climate that works then I will eat humble pie and stand corrected.

However, even if it works it is a lot of effort to chase diminishing returns given all the other emissions and impacts that we need to sort. Some would argue that even PH is a step too far.

Nick

[Tom Foster]

I wonder what 'This' was tried? I wonder if it was really the same as my 'This' – would it be interesting to
a) check further into my 'This'
b) illuminate rather than dismiss?
So far, I'm none the wiser from your words.

[Mark Siddall]

Ahh, thought that you may be back to this one Tom 🙂
Is this what you're thinking? http://www.artistsdomain.com/dev/eere/web/1940.html

From what you say it is not so much that you are interested in “beyond” as “an alternative to.” I can appreciate your hesitation – took me a while to determine what I consider to be the most plaustible approach. Though I saddly fear that you will not get the results that you're looking for – not affordably and reliably at least, for modelling this kind of animal you may want to move up a notch and have a look at Trnsys http://www.trnsys.com/

If you want to save a whole bunch of time and money you could read:
“New Inventions in Low-Cost Solar Heating: One Hundred Daring Schemes Tried and Untried” by William Shurcliff (1979) – Here, Shurcliff, a physicist, is very interested in solar
then contrast that against, “Superinsulated Houses and Air-To-Air Heat Exchangers ” by William Shurcliff (1988) – Shurcliff is now wise to the failings of solar and has spotted a bright new approach called superinsulation that comes up trumps.
and then if you still insist wrap it all off with “Solar architecture in cool climates” by Colin Porteous (2005)

Okay, so the examples are not all in the UK and they are not all “just as you're thinking” but there is a weight of evidence to suggest that in cool climates such as the UK these concepts have no real long term application (from an architectural perspective the building gets lost beneath the panels – where is the joy of living and the quality of life?)

Mark

About William Shurcliff http://www.washingtonpost.com/wp-dyn/content/article/2006/06/27/AR2006062701675.html

[Nick Grant]

Tom

Perhaps best to try this out on yourself rather than clients.

Feel free to ignore us, no axe to grind just an overpowering sense of deja vu C 1980.

Good luck

Nick

[Tom Foster]

I'd really appreciate it if you'd say briefly what things happened c1980 that you're retroviewing now, so I can check whether this now is really the same – because I don't feel I've given you much to go on so far.

[Tom Foster]

Is this what you're thinking? http://www.artistsdomain.com/dev/eere/web/1940.html

My god! – not remotely!

the building gets lost beneath the panels – where is the joy of living and the quality of life?

It's specifically done without dedicated panels, to get away from 'bolt on technology'. The architectural art of it is to find ways to make the solar building look (near) normal but with a hint of 'something interesting happening here'.

Suppose it's too much to wish that someone would say ' tell us more, Tom'. Even tho a faithful AECB member, I feel like an unwelcome intruder, rocking the boat.

[Tom Foster]

Is this what you're thinking? http://www.artistsdomain.com/dev/eere/web/1940.html

My god! – not remotely!

the building gets lost beneath the panels – where is the joy of living and the quality of life?

It's specifically done without dedicated panels, to get away from 'bolt on technology'. The architectural art of it is to find ways to make the solar building look (near) normal but with a hint of 'something interesting happening here'. Luckily the client wants the building to look like I've designed it anyway – whether it works fully or partly solar-wise will be interesting to us – will it be to you?

Suppose it's too much to wish that someone would say ' tell us more, Tom'. Even tho a faithful AECB member, I feel like an unwelcome intruder, rocking the boat.

[Nick Grant]

Tom

You are raising an interesting point about how your ideas are received differently on this forum. Perhaps that is because it is moderated by the Passivhaus Maffia or perhaps there is another explanation . . .

I did say tell us more, ie give us some evidence that it works. I don't however have inclination to follow lots of links or read through long documents if my judgement is that it won't fly. Happy for that to be my loss if I am wrong but life is too short to follow up all avenues.

So if you want to get hard nosed AECB members interested you need to present a sentence or sketch showing what is different about your approach. You should be able to demonstrate that it should work by building physics which I'd suggest you will need to understand before using any dynamic model. However if I were you I'd be seeking people who can show me why my idea doesn't work rather than people who are supportive. Once you know it works then seek out the supportive ones, ideally people with more money than sense, anyone who can help make the proven concept a reality.

As an asides, what I think was found with most attempts at solar was that unless you plug the leaks, the feeble winter gains vanish. Hence all the modern emphasis on sorting thermal bridges, window details, air leakage etc etc. This is the journey Mark and I and thousands of others have been on.

The problem with trying to grab excess heat (to compensate for sloppy details as you seem to suggest) is that when the sun is shining, how to store that without either using more primary energy than you usefully gain (pumps, fans etc) or cooking the occupants.

That is a quick summary of why I'm jumping to conclusions about your ideas and not something I want to discuss further.

If I were in your situation I would spend my money on a couple of hours consultancy from a good energy consultant/building physicist rather than software. Or write up your proposal as a paper and put it out for peer review. If you really believe in your ideas then such an investment in time and money would be quite trivial (and no I'm not a properly trained physicist or looking for the work).

If you really have come up with the next great thing in low energy building design I will happily change my mind (as I am forced to do on a regular basis).

So back to your original question I'd say start with the simplest building design possible and a pocket calculator or Excel as you need to understand what is going on without fooling yourself with hidden assumptions or internal errors in a black box computer model.

The reason I'm taking time to engage, at the real risk of being disliked or considered arrogant by you and others, is that I'm passionate about the whole process of filtering ideas and spotting stuff that is likely to work or not. If I put my ideas out there it is always nice to have people agree but always more valuable to be shown I am wrong before I waste a significant chunk of a short life pursuing another dead end.

We have been here before so nothing else to add. Happy to meet up at EcoBuild and look at plans over a coffee.

Nick

[Tom Foster]

That answer is greatly appreciated Nick, and so was Mark's most recent one.

Lots to follow up there; already engaged in some of your suggestions; in addition seeking informal engagement (including engaged disagreement – yes please!) here, on GBF etc.

Just to say, now, that I'm as 'passionate' as you to 'plug the leaks' in all the ways that PH has so effectively prioritised. No way I want to supersede or replace that, and there'd be none better than the Institute to take on some of the ideas I'm proposing, as an evolution of PH.

True I'd like to be able to 'spend' some of my increased/manageable/stored solar heat on slightly relaxing the stringencies of PH-required workmanship and in-use discipline – but that's optional/red herring – wish I hadn't mentioned it!

If you say 'it's been tried and failed before' maybe 'before' was without the benefit of recent development of PH or (near-PH) 'leak-plugging', which I agree is indispensable, to reduce heat requirement to within range of UK-weather solar heat availability during the heating season.

[Nick Grant]

Tom

I said nothing to add but goal posts moved!

You have mentioned before what you wished you had not mentioned this time and in no uncertain terms. The idea that PH requires such rigidity and construction care, which it does.

If however you are proposing PH + clever solar then yes I am sure something could probably be made to work, perhaps not for 100% but could shave of another 5-10 kWh/m2.

This takes us back to Mark's point, bigger fish to fry. Say you do get to 0 kWh/m2 space heat. Assuming a 100m2 (larger than average UK but modest) then you save 1,500 kWh/year. Say 5p/kWh = £75/year. Hopefully your system uses no pumps or fans and has no operating cost or maintenance requirements.

So what is the extra cost of your system likely to be? Is it the best use of resources? What are the risks such as overheating?

[Tom Foster]

AFAIK what I mentioned before 'in no uncertain terms', was about Interseasonal/continuous storage of masses of summer heat, which will allow future relaxation of the loss-reduction imperative, and will reintroduce the possibility of more indented-envelope, glassier, lightweight, simpler-built buildings – Buckminster Fuller again, perhaps – because the necessary massiveness will be remote (or just underneath) the above-ground building.

That's a future project – I-ZF – Interseasonal Zero-Fuel; for now I've imported much of the ways-and-means thinking that's gone into that, into achieving surprisingly much of the aims of I-ZF, but by short-cycle capture of heating-season (not summer) solar heat and storage of same within above-ground PH-style fabric (not remotely/beneath), and by prolonging the storage duration there, from 1.5 to 2 days, to nearer 10 days.

As it's shaping up, collection should be by natural-convection means, transport at variable volume proportional to current solar intensity, by PV-powered fan or pump (depending on chosen thermofluid). Extra-cost apparatus looks to be minor – mainly a matter of re-arranging fabric elements you'd mostly be having anyway.

The ultimate prize would be complete elimination of backup heating system, for what that's worth. Or at least minimised call on same, if the backup were just an electric element in the MHRV. Or maybe keep that woodburner anyway, for the January black-hole!

[Mark Siddall]

Hi Tom,
I'm increasingly thinking of David O's house (where is that up to?) His home, I believe, has PH concepts in it's sights but totally dispenses for heating by being free running and requiring a jumper or two when it gets tough.

Similarly if you, or your client, are willing to compromise comfort standards (20C) and accept a free running space then perhaps you can tap into some solar energy. But if comfort can not be compromised then please be aware that PHI have undertaken dynamic modelling that shows there is little to be gained from thermal mass during the winter – in fact as a result of hygrothermal conditions (judging by detailed analysis for southern Europe) you can have to much mass which can actually increase the heating load during the winter – which is not a really a good idea as I'm sure that you appreciate (As I understand it most dynamic modelling tools (IES, TAS and even TRNSYS for that matter) do not include for the influence of hygrothermal performance and as a consequence comes out with results that favours mass more strongly).

Cheers,
Mark

[Mark Siddall]

Some data on David's house can be found here http://products.ihs.com/cis/Doc.aspx?AuthCode=&DocNum=201819 (you should be able to find the doc for free online from EST)

In the PHI study the modelled low, meduim, high and super heavy mass (actually it was Jurgen Schnieders Phd thesis – he has been likened to being the pope building simulation). More mass (concrete), means more moisture storage. Evaporation of absorbed moisture in winter (low internal RH) becomes a heat load rather than a heat gain i.e. phase change in the winter is not useful. So the advantageous out-of phase emission that you suggest is reduced to the to point where it consumes more energy than the building with less mass (i.e. high is better than super heavy).

Hygrothermal is not the whacky fringe – dynamic hygrothermal tools like WUFI are about as advanced building physics it gets. “All” PHI did was include that set of physics within their modelling techniques (using such modelling they can in form how PHPP is develop).

Mark

[Tom Foster]

That's v informative, thanks Mark.

I understand that much moisture has been stored into the mass during summer, when often internal RH and certainly absolute air water content is higher.
I understand that that summer equilibrium gets adjusted down to lower moisture content in the mass, when the heating season comes and internal RH often and certainly absolute air water content is lower.
I understand that there could be a heat demand in effecting that transition, going into the heating season (but presumably that means there would be a heat contribution towards the end of the heating season?)

First point – it seems to me that that heat demand would be a one-off, albeit maybe a prolonged one, of gradual re-equilibriation during the beginning of the heating season. I don't see that humidity fluctuations during the heating season would then continue to be a nett heat demand, exacerbated by larger mass creating larger quantities of stored moisture to be shifted.

Second point – you say that the beginning-of-heating-season re-equilbriation would be by evaporation. Are we saying the summer moisture has been stored into the mass by condensation to liquid? Or is it held in there as vapour, which wouldn't then have to be 'evaporated' but would merely move out driven by partial vapour pressure, which I think would create no external heat demand?

[Mark Siddall]

Tom,
Go read the Phd and/or find a simulation tool as accurate as PHIs Dynbil. I'm not going to talk around the houses on this.

Mark

[Tom Foster]

whooof

[Mark Siddall]

Not sure whether you're trying to make a dog noise or what. Wasn't trying to be inflamatory. There is a point where the discussion of theory ceases to intreague and I like to see the numbers (often trying to do them myself – sometimes with more success than others). A nice quote that I came across recently:

“Get the habit of analysis – analysis will in time enable synthesis to become your habit of mind.“ Frank Lloyd Wright

Mark

[Anonymous]

Trying hard to follow this thread…. Are you not looking at the “trombe wall” simple model; but possibly with controlled ventilation across. Moving onto a more techological approach, there are lage commercial projects which have looked at using the ground beneath the building as a thermal mass to store energy (the ground being insulated to some depth around the edge of the building). Would this not be more suitable in a domestic dwelling?

I have just recently looked at a highly glazed unheated sun room on the side of an existing building to be used as a heat source to the main building. The building is an existing cottage (very poor insulation); however the calculations do suggest that you can get some heating from the sun room into the house during the mid-seasons – effectively the trombe wall principle. As I say this was not a very well insulated building.

To get the sort of mass you are implying for inter-seasonal variations, I guess the option would be the ground below.

[Tom Foster]

Yes, as noted in my post of 21 Jan above, interseasonal I-ZF would store into the uninsulated ground nearby or beneath (with 'wing' insulation) but that project's presently mothballed.

So am meanwhile interested in 'extended short-cycle' storing into above-ground building fabric, especially as massive as is typically found in older buildings. Trombe with air movement is one of the several ways envisaged, to collect solar heat. Conservatory is a variant on Trombe, with a moving-air collecting cavity battened off the face of the house wall on which the radiation falls, rather than collecting air from the conservatory space itself. The trick is to maximise temp of take-off air, harvesting the temp peaks and rejecting the troughs, as cloud comes and goes, across the sun. That way, the considerable momentary power of the sun can be harvested while it's out, rather than averaging it down to daily-mediocre.

How would your conservatory have contributed to a near-PH insulated/airtighted/MHVR'd house? Would that extend the benefit deeper into the winter season?

[Nick Grant]

Maxwell's Demon!

🙂

[Anonymous]

Fostertom,

With the poorly insulated house, the sun room provided useful heat to the adjacent room – during March/April/Oct/Nov periods the temperature in the adjacent room was maintained at around 20 deg C from around noon to 6pm with a gradual slope either side. The key factor was the air flow between the two rooms – effectively open doors between the two rooms worked well; the use of smaller vents (ie high and low level vents) did not provide sufficent energy transfer. This was a very poor insulated double height room – a PH standard would need much less heat energy and therefore the (1) air flow from the sun room to the adjacent room could be reduced and (2) the lower energy transfer would provide greater impact on the air temperature.

The sun room benefited from solid stone wallls on the rear elevation (facing south) and a solid floor. The thermal mass helped to alleviate peak temperatures in the summer (around 35 deg C peak). Even in peak winter, the floor temperature remained a few degrees above the air temperature in the conservatory (still cold but possiblities?).

I will need to look at the model again and run a simulation with a PH standard construction for the main house.

To get longer short term storage, one idea may be to use the “Thermodeck” approach with air flow within concrete tubes to precharge the tubes during warmer periods. This effectively increases the amount of thermal mass as it allows single flow of heat through the mass. I am thinking of a concrete section facing south with the air flow internally. The air then cycles one way from the sun room through the tubes to heat them up and then to the living area. If a quicker response is required the air can be diverted before the tubes directly to the living area.

Just an idea. I think key items will the the thickness of the concrete and depth of the sun room in relation to the possible
heat ouput.

[Tom Foster]

Maxwell's Demon!

If you think that, I can see the flaw in it – can you?

[Anonymous]

Some rough figures for you. Based on one day in early April – the main room achieves a peak of around 20deg C with the openings open; with no air movement the room air is around 12 deg C. The external air temperatue is around a peak of 10.5deg C but with far greater fluctuation. The actual sun room is around 1-2 deg C greater than the air temperature of the main room (with no air movement between the sun room is around 10K greater).

From this I see that the heat conduction is minimal through the internal wall – due to the high thermal mass (350mm thick solid flint/stone) and the main heat transfer from the sun room is via the air movement between the two areas.

The thermal mass is providing a stabilising factor on the air temperatures (as you would expect) but not assisting in heat tranfer through. In this model, both the room and the sun room have a high thermal mass which may be affecting the temperatures – i.e within the main room it takes longer to get up to a comfortable temperature. A PH standard house will probably perform quicker.

The mass of the internal wall is helping to store heat within the sun room along with the floor. If you insulate the wall to the sun-space then the aitr temperaute in the sun space will fluctuate more. You would then need to pull the air from the sun space acorss the insulated store and then into the main room – or with simple controls back into the sun room depending upon the requirments in the main room. If you looked at a more technical approach you could use embedded pipe coils within the wall which then circulate the heat either into the concrete mass or a cylinder. This would be very low grade heat for a cylinder though.

[Anonymous]

Steve,

I was first told about this study 10 years ago, therefore I think it may of been before Raslan's work (was he looking more at Part L compliance software rather than general simulation?). I did recieve another mention of the study, maybe the same or another one, a few months ago..I am sure there was something in the CIBSE Journal or simlar on this. I will need to look around and try and find out….

[Author]

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