# MVHR + solar



## about2build (22 Sep 2011)

At design phase of my building and was wondering what peoples opinions would be on whether an almost passive house combined with mvhr and solar panels for hot water is workable. With an airtight house heat recovery ventilation is a must for air quality plus the space heating load should be minimal. Solar panels should supply hot water for the summer but will I need a wood burning stove with back boiler for the winter months or in case of power outage? 2600 sq feet 3 en suites and main bathroom. Any thoughts greatly appreciated


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## onq (22 Sep 2011)

I'm very wary of MVHR for the moment on three grounds -

(i) transmission of cold smoke and fumes from a developing fire emergency to sleeping occupancy.
(ii) transmission of fire through the ductwork past the plasterboard offering the 30 minutes FR
(iii) transmission of sound from room to room.

I'm wary of a 60-year construction lifespan.
I'm wary of external insulation without a cavity.
I'm wary of the longevity of self-coloured renders.
I'm wary of the longevity of render without a masonry substrate
I'm wary of the cost/benefit/payback time of anything with a panel or a pump or a windmill.

I'm wary of the whole ethos of 'sealed living' - we'll all become wallflowers, unable to deal with draughts, chills, cold breezes.

Passive design solutions with good glazing orientation and internal massive heat stores are a good way forward.

ONQ.

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## about2build (22 Sep 2011)

Im going passive and my glazing orientation is south south west with few windows on North....what is the internal massive heat store you speak of or would recommend?


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## quentingargan (23 Sep 2011)

I personally have had enough of my life living in draughty houses. I built a house recently in the eco-village in Cloughjordan using Durisol blocks - they provide high internal heat store in the internal concrete layer, while providing external insualtion "within the block" so to speak. After that, draughtproofing is down to detail. 

Your solar panels should probably be tubes if you are building near passive. You will want hot water from this system on the fringes of the season, to prevent having to light your stove or use electricity in the spring and autumn months, and vacuum systems are better insulated and work better on the fringes of the seasons. A steeper pitch of roof (say 45 or 50 degrees) would be better for spring and autumn solar output, but will reduce summer - which, if you are over-sizing the panels, may be a good thing. I would definitely use a heat dump on the solar circuit if you are doing this, regardless of the type of system you use.


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## onq (23 Sep 2011)

about2build said:


> Im going passive and my glazing orientation is south south west with few windows on North....what is the internal massive heat store you speak of or would recommend?



Insulation is low mass - mainly air held in cellular structuers- and doesn't store of transmit hear.
Concrete is as massive as it gets and is a monolithic structure which both stores and transmits heat.

If you were to face concrete with a dark stone directly bedded on it, like slate or granite, and allow the sun to shine on it it would gradually heat up.
When the sun shone elsewhere or went down, it would be likely to emit the heat, like a heat store.
So a living space with a dark stone floor could contribute significantly to the ambient heating of the house.

Conversely, allowing sunlight to shine on a relatively cellular material like a floating timber floor, i.e. one that is separated from the floor slab, will fairly have instant warm up, but equally quick heat loss and may contribute little or nothing back by way of releasing stored heat to the room
Light coloured timber would be the least absorptive and emittive.

Colour and mass are both important to a heat store in Ireland where the highest temperature may be in the high twenties.
Light-coloured stone buildings are effective heat stores in very hot countries.
Because the heat store is within the insulated envelope of the house, its a nett heat gain every day, with a slow release at night.

The slab is faced with dark material - I have suggested stonework - and insulated at the sides and below to prevent cold bridging leeching the heat our of it.

I hope that offers some insight into it.
This is the theory as I understand the matter BTW.
I cannot point to any worked examples I have done myself.
Happy to stand corrected by those claiming to know more on this.


ONQ.

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All advice on AAM is remote from the situation and cannot be relied upon                                  as a defence or support - in and of    itself  -         should       legal        action    be      taken.
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## onq (23 Sep 2011)

quentingargan said:


> I personally have had enough of my life living in draughty houses. I built a house recently in the eco-village in Cloughjordan using Durisol blocks - they provide high internal heat store in the internal concrete layer, while providing external insualtion "within the block" so to speak. After that, draughtproofing is down to detail.



Very interesting material - I've glanced at the website.

What kind of fire rating might one expect?

ONQ.

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All advice on AAM is remote from the situation and cannot be relied upon                                  as a defence or support - in and of    itself  -         should       legal        action    be      taken.
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## about2build (25 Sep 2011)

@quentingargan thanks for the input and ya I'm 100% in agreement on the draught free air tight building.... you propose solar tubes but are they more expensive and easier to damage? Also I like the idea of using a heat pump for the solar panels.....would this water be pumped through UFH or rads and if so would that not rob the house of DHW?


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## about2build (28 Sep 2011)

What u-value would one expect from these insulated blocks?


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## quentingargan (28 Sep 2011)

about2build said:


> What u-value would one expect from these insulated blocks?


There are tests pending, but it is expected that the U value will be [FONT=&quot]0.19W/m2K 

Not as low as some systems, but I think the thermal mass makes up for that.. 
[/FONT]


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## onq (29 Sep 2011)

I've found the link to fire resistance

http://durisolbuild.com/concrete-homes-shtml/

_"The Durisol wall system has a 4 hour fire rating. The surface burning characteristics of Durisol far surpass all other types of ICF products.Dursiol has a flame spread and smoke spread rating of zero. Unlike foam, Durisol will not ignite, melt, sustain fire or release toxic smoke in the event of a fire. - Over 4 hour Fire Resistance Rating - 0 Flame Spread - 11 Smoke Spread - 0 Fuel Contributed to fire. __Test Reports are available upon request."_

I don't understand the smoke spread rating or the 4 hour fire rating - the block look like hollow block, which in a concrete hollow block might offer a 1-2 hour fire rating (= a combined 90mmm of concrete).

ONQ.

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All advice on AAM is remote from the situation and cannot be relied upon                                   as a defence or support - in and of     itself  -         should       legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                                   Real Life with rights to inspect and    issue         reports    on     the         matters    at      hand.


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## about2build (27 Oct 2011)

@quentingargan thanks for the input and ya I'm 100% in agreement on the  draught free air tight building.... you propose solar tubes but are they  more expensive and easier to damage? Also I like the idea of using a  heat pump for the solar panels.....would this water be pumped through  UFH or rads and if so would that not rob the house of DHW?


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## quentingargan (28 Oct 2011)

The tubes are generally about the same price as flatplate, but will need replacing after about 20 years, whereas a flatplate should last about 40 years plus. That said, the flask system has tubes that are very cheap to replace. 

Yes tubes will break more easily, but they are easy to change. If you ever do happen to break a flatplate, it'll cost yer!

I'm not an advocate of using any solar panel for space heating, with or without a heat pump. They don't collect enough energy to make a useful return on the capital cost. Others would differ on that score.


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## Lanni (17 Nov 2011)

You do know that it is possible to integrate solar collectors, stoves and heat pumps with the MVHR system, which would save money on underfloor hating and radiators. This is the situation for passive houses. Make sure you calculate the heat load of the building using PHPP or DEAP, as you might need a secondary backup system.

You can also use low temperature radiators instead of an underfloor heating system to emit heat from the heat pump.


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## lowCO2design (17 Nov 2011)

Lanni said:


> You do know that it is possible to integrate solar collectors, stoves and heat pumps with the MVHR system, which would save money on underfloor hating and radiators. This is the situation for passive houses.


is that so? or is it a case that it has just not been tried yet? 
this gives an example of '3 separate heating devices' installed and commissioned 
[broken link removed]


> Make sure you calculate the heat load of the building using PHPP or DEAP


+1
About2build - are you going to give us a kWh/m2/yr or with all this passive house talk has a PHPP calculation even being carried out on the design? or even a provisional BER?


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