I have to make a decision pretty sharpish about whether to put in IWI or not. The house is on 3 floors (150m2 each, 3m high) here in Italy and I have already installed a very effective and economical wood-burner, together with PV, Solar and a new well insulated roof with ventilation on the cold side to reduce solar gain in the summer. Both the top floor and most of the bottom floor could have IWI installed over the next 6-9 months and the walls, floors and ceilings on these 2 floors are currently unfinished.

The issue I have is that the heating works, and pretty cheaply too; instead, our quality of life is affected by how hot it is in the summer and I cannot risk increasing the current summer day/night maximums (26-28 dec C) - I wish I had taken more notice but I think the internal diurnal range is around 3 degs during the summer. Normal max shade temp about 35-38 degs, min night temp 20 deg. I have a very large extractor fan (over 2m3/sec on max) in the roof over the stair well which comes on when the external temp is below the internal temp. Ground floor has 50cm thick walls, middle floor 40cm and top floor 30cms, made of solid but light(ish) stone, concrete beams and blocks (floors and roof).......and loads of cement. Rear of bottom floor is underground ,embedded in bedrock.

Everyone 'knows' that one shouldn't fit IWI to a heavyweight house but what is the impact if you do? Budget and space reasons mean I am looking at 50mm or less under the plaster. I 'want to' put it in not least of which because it should prevent the condensation/mould issues we currently have on the middle floor occurring on the ground/top floors.

Summer routine is well established: sun shalt not touch glass (external shutters), all openings shut when hotter outside, all openings open when it cools - fan on, so this thread is just about what happens in the summer with IWI in a heavy house. All thoughts most gratefully received.

If asked, my gut says put it in in the ground floor but not on the top floor. Reason is I am making an apartment on ground floor, back wall of which is internal ie would not be insulated but the other part of this floor is unheated (plant room etc) always cooool as back wall underground. WhatdoUthink?

Woodfibre insulation?
gives a high decrement delay so should be ok summer as well

And ideal humidity for health

Neilgorswift, yes I had thought I should look into woodfibre insulation but more because it provides a buffer for humidity, trouble is price: 4 or 5 times more I think. Can you say a little more about the decrement delay comparison - say 400mm of light stone Vs 50mm of woodfibre insulation - I know it is heavy stuff but are they really in the same ballpark?

Hi,

I did some thermal modelling of thermal mass situations some time ago. The options I looked at were

Solid stone U value 1.6W/m2K (Control)
Insulated Cavity wall U-value 0.2W/m2K
Externally Insulated masonry wall U-value 0.2W/m2K
Timber frame U-value 0.2W/m2K

Not exactly the same as your scenario though the lightweight timber frame option results give an indication of the difference between internal comfort conditions for relative heavyweight lightweight scenarios. Though results are for UK climate

Maybe worth £1 here http://www.greenbuildingpress.co.uk/product_details.php?category_id=9&item_id=233

Or its also in the Green Building Bible Vol 2 if you have a copy

Posted By: Gotanewlife

Nevertheless, Pugliese to answer your questions: no DPC; stone very, very soft, hygroscopic, dusty, rendered externally and painted with breathable masonry paint; top and bottom floors each have several

Hi Gotanewlife - I am not as technically competent as most on this forum and tend to just try to apply some common sense to problems such as these.

It sounds to me that your wall construction is similar to tuffo and i have a mate who has fitted IWI to a tuffo house, in an effort to cut heating bills, so I have asked him for his experience this summer.

My own experience with my stone house (limestone,min 1m thick) last summer was that the house was unoccupied until mid August and outside temps during the day similar to yours, but with the house shaded and unoccupied, when I arrived the internal temp was a cool 18c. However when we left 2 weeks later and despite following your regime of keeping shutters closed etc the internal temp was up to around 24c and would not drop. The only thing that made it more comfortable was reducing the humidity. My obvious conclusion therefore was that it was us and our activities that raised the temp and having IWI would just help to keep that heat in. Now I could be wide of the mark and would be interested in what the more technically minded folk make of it.

Will report back if I get a response from my tuffo man.

Posted By: PuglieseHi Gotanewlife - I am not as technically competent as most on this forum and tend to just try to apply some common sense to problems such as these.

You and me both!!!! - I use common sense and gut instinct but then cover it with a thin veneer of bullshxt - seems to work usually.

And you're right - all external walls are tuffo and the big load bearing one down the middle of the house upon which all my beams rest. You're are also right about humidity being a critical comfort factor however during the summer I seem to have low or too low humidity. Your real life outcome from putting IWI in is exactly what I feared and I guess I can't take a risk since we already break the 28 deg internal temp barrier occasionally, which for us is the maximum acceptable. I do so much hope you can get a response from your tuffo man.....

Posted By: Sprocketwe don't have anything like your outside temperatures so we've never needed to shade the windows. If we get enough solar gain through the 3G (rarely happens I think) then the MVHR goes to bypass

Here we can never use by-pass or any type of ventilation from 10 am to 7 pm (both variable a bit) as the outside air temp is MUCH higher than the air temp. I'm afraid air-con is not an option - with about 1200m3 of living space small becomes rather relative, and lecky is dammed expensive as would be the air-con units, I sell my PV at about 18 cents/kWh so that would be the lost opportunity cost. Thanks for your input, I guess this is just one of those areas where members UK experiences just don't translate well enough to help me.

Just wondering if there might be MVHR that works in reverse when required - it wouldn't help the heat but it might allow ventilation....

Posted By: GotanewlifeJust wondering if there might be MVHR that works in reverse when required - it wouldn't help the heat but it might allow ventilation....

A counterflow heat exchanger is just a plate with one end at indoor air temperature & the other at outside air temperature. If the inside is warmer than outside it helps to retain warmth & if the inside is cooler than outside then it helps to retain "coolth". So it can help to provide cool ventilation on summer days when the shutters, windows & doors are closed.

You can install an MVHR unit with a ground-glycol-air heat exchanger on the fresh air intake. This is effectively a pipe buried in the garden, filled with glycol fluid & connected to a radiator on the fresh air inlet. It provides frost protection to the heat exchanger in winter & comfort cooling in summer in combination with the heat exchanger summer bypass. There are no compressors to run, just an extra pump to circulate the fluid.

David

blockquote> I do so much hope you can get a response from your tuffo man.....

Just spoke to Tuffo man and unfortunately he has yet to finish his IWI but he thought it would keep it cooler. After some discussion we agreed that it would only keep it cooler if your interior is heated by energy coming through the wall. Heat introduced by air coming through open doorways, occupants, cooking etc will be retained for longer with IWI, as will any chilled air if you go for any form of cooling. So best nil cost solution during summer is just keep the house closed up and in the dark, and do all your cooking and living outside. If the back of the ground floor is in bedrock why not build a summer bedroom there? Ciao

Where in dear old Italia are you?

Very Nice - my wife loves it around there, alas not for the scenery, but heading towards the Adriatic coast towards Civitinova Marche is where all the shoe and handbag factories/outlets are - I would be broke within a month

We are further south and have restored a Trullo near Alberobello with about 80 olives and assorted fruit trees. www.romanticpuglia.co.uk Integration is the key and above all the qualities of life living in Italy brings, we value the people the most - they are just so friendly, generous and welcoming.

Anyway, to go back on thread, i am very interested in how MVHR can be adapted/used to help overheating and humidity. We have plans to extend the trullo this winter and whilst this will be built with modern well insulated methods of construction and have made sure we maximise the use of passive solar (big walnut trees in front of glass - shade summer, winter sun), the new extension could overheat and I think the main structure will definitely benefit from having the air changed. Currently thinking along the lines of having the MVHR inlet underground as highlighted by Davidfreeborough above. However, I want to understand more about MVHR and have just opted for a self install of a VA Kinetic Plus in our house build in the UK, being overseen/commissioned by a ventilation specialist. Once I have done that I will try and design a system for Italy - no doubt I will be back on here for advice from the true experts

Posted By: PuglieseCurrently thinking along the lines of having the MVHR inlet underground as highlighted by Davidfreeborough above.

There are two main ways of using the ground to pre-heat &/or pre-cool the fresh air inlet to an MVHR unit.

A ground-to-air heat exchanger passes the air through an underground duct. This avoids additional pumps, but you need to make sure the duct falls towards a drain to avoid pooling of condensation & that it is accessible for cleaning in case it gets mouldy.

A ground-to-glycol-to-air heat exchanger passes glycol fluid through an underground pipe & uses this to feed a radiator on the fresh air inlet. This simplifies the ducting & avoids any concerns about mould, but requires a pump to circulate the fluid.

In both cases, the amount of cooling is limited to a few degrees, but this can be very useful on a hot day.

See the following page for an overview:

http://www.greenbuildingstore.co.uk/page--comfort-ventilation-mvhr.html

David