[Mark Siddall]

Rachel,
I've not used Psi-therm but I know a man that has. Apparently it is (now) quite good. Some teething issues on translation may still occur but from what I hear they are quickly responded to.

Mark

[Mark Siddall]

David,
The main thing is that you are consistent and use good QA so that records of the calculations make them replicable. (The thermal bridging calc is just a correction factor.) I would suggest measuring to the underside of the concrete.

Incidentally, it is not best practice to place the insulation over the top of the concrete as you can get moisture and mould growth. (Place the insulation beneath.)

HTH,
Mark

[Mark Siddall]

Tom
It sounds like you should get PHPP and give it a whirl.

Mark

[Mark Siddall]

JSH,
The AECB is pretty busy with its online presence – e-newsletter, soap box, carbonlite (though these courses opperate in RL for now), and of course the forum. The forum has slowed down over the last few years – in part because there has been further (excessive?) diversification by members, and the AECB development team, into other social media such as Facebook and Twitter. Are you suggesting that members should be encouraged to use the forum rather than Facebook and Twitter?

Mark

[Mark Siddall]

Simon,
Open, closed, naked, sleeping, shading, ventilation. It all sounds to complex to me. A computer controlled system is, in my view OTT. Why not let the occupants choose how they control the shading? They will know best what they want and this can be controlled by a simple switch and a mechanical control on the shading.

Mark

[Mark Siddall]

Alan/Nick,
I've been looking over the Lunos website. The Lunotherm unit looks pretty good http://www.lunos.de/?page_id=282&lang=en The advantages is that, with it being a through the wall unit, air flows can be measured more easily. The challenge with this unit could be, in some cases, that it has been designed for external insulation.

The challenge with trickle vent supply (say http://www.aereco.co.uk/products/air-inlets) is that finding a hood that can go over.

[Mark Siddall]

Peter,
I've been reading a PhD on indoor air quality in New Zealand homes; the standard house type is a bungalow. The studies undertaken suggest that PSV does not work as there is not enough stack. Wind is the dominant driver of air changes. The PhD quite clearly showed that

1) More than 1.25 ach/hr is required to maintain IAQ when using natural ventilation options; and even then it is not ideal. These findings were supported by on site measurements in a number of homes throughout the country. (In the study, for the passive stack option, between 80,000mm2 and 105,000mm2 of trickle vent and stack ventilator were required dependent upon local climate.)
2) Unheated naturally ventilated bedrooms suffer from even less ideal IAQ as stack effect is not suitably exploited.
2) When using MEV or MVHR it is benefitial to have improved airtightness. The study examined airtightness standards down to an n50 of 1 ac/h. As airtightness improved so did the effectiveness of the ventilation strategy. Under this scenario 7.5l/s (0.5 ac/h) proved acceptable.
3) between MEV and MVHR, MVHR – as balanced ventilation – displayed the best opportunity for ventilation effectiveness (regardless of airtightness.)
4) MEV trickle vent area for the house was 15,400 mm2. 100m2 3 bed home. This was maintained for all airtightness options ranging between an n50 of 1 and 6.5.

Whilst demand led scenarios were not explored in the PhD I hope that this is of assistance.

[Mark Siddall]

In my experience tanking of the insulation can be achieved by the careful appilcation of a bitumenous paint.

[Mark Siddall]

Kate,
If we have to build then, on the whole, I do still tend to favour the idea of using timber. My post was just to reinforce the case for ensuring that timber is sourced from a carefully managed forest that plants more trees that it cuts down. (No doubt a good chunk of the “carbon debt” that I allude to is also shouldered by farming etc. )

Mark

[Mark Siddall]

Could you not create a stuctural thermal break using a product such as the Isocorb KST connector? http://www.schoeck.co.uk/upload/documents/flashbook/en_gb/schoeck_isokorb_/specifiers_handbook_12-10-17_2663/index.html#/14/

[Mark Siddall]

Tom,
Have a look at https://aecb.net/forum/index.php/topic,1962.msg8570.html#msg8570

[Mark Siddall]

Yes. It does matter.

[Mark Siddall]

Cats? On AECB? It's surely not environmentally friendly to keep cats, all that extra food, all those poor dead birds, worse than kids aren't they?

Anyway, most of the ones I've seen on eBay seem to be accurate to within +/- 2C, is that worthwhile?

Cats seem to be accurate to within +/- 2C?

[Mark Siddall]

It would appear that Kate has been spending to long with a certain mechanical engineer 😉 …..She is correct in suggesting that the thermodynamics of the heat exchanger means that the warmer air offers little benefit. The main benefit of earth tubes with MVHR is avoiding the need for frost protection with a high primary energy demand, however, in the UK the climate is not so demanding as to warrent the capital expenditure. (The cost benefit analysis that I have seen – for more ideal climates than the UK – suggests that because of earth tubes are not worthwhile.)

Technically cooling can be provided via the earth tube in the summer, but in the UK you may as well just open the windows (there are other posts on this forum that discuss the balance point temperature for when it is ideal to open/close windows.)

You can get some earth tubes coated with silver to reduce the risk of mould growth. You need to ensure that they are laid to falls, with a sump and suitable drainage. Also, there have been instances, apparently, whereby the water table has risen and filled the earth tube to one degree or another.

For the frost protection of the MVHR system a ground loop filled with glycol (and linked to a small pump and water to air heat exchanger) may be more appropriate than an earth tube – shorter lengths, less excavation, reduced cost, less risk of microbial gunk and less risk of flooding- ,however, it may still prove uneconomic (should that be an important consideration). It could also be used to achieve limited cooling in the summer (though opening the windows is still a better option.)

[Mark Siddall]

Dave,
Well noted. In that case I have this particular research wrongly associated with what I saw in Hannover. The work presented at the conference was considerably well developed – it heard about samples of flexible ultra thin glass (0.3mm?) and saw photos of a glazing unit in a frame system. Pretty impressive.

….sounds like this other lot have some catching up to do.

[Author]

Posts