Thatch , oh yes , its cool in summer and warm in winter.

[robgil]

I have heard this so many times now however i am about to put this myth to rest.
this is how it should read.
Thatch , its bloody freezing in the winter and absolutely boiling in the summer.

Its 26 degrees in here , its cooler outside.
all my windows and doors are open and ive got a fan on.

Thatch is a great insulator, in the summer.

 

[ian]

Maybe you made a simple error - if you open all the doors and windows you let in all the warm air from outside! , though I suspect you have enough airflow sources anyway. You have no control over the temperature of draughts from a window.
Try draughts from a keg and you may find a more satisfying result.

 

[Penners]

The trick is also to run your central heating in winter and your air conditioning in summer.

Not the other way around.

 

[worms]

Have you checked that your roof isn't on inside out?

 

[robgil]

no , but i did sleep in the fridge last night cuddling up to a bag if crispy salad.

 

[Ushy M]

Rob, late reply from me - have been in the wet and windy West Country for a few days.

Yes, we always laugh (hollowly) when we're told how thatch is warm in the winter and cool in the summer - our experience is that it's absolutely freezing in the winter. However, this is the first time in the five years we've been here that the house is actually warm enough (No fleece! no socks! no going outside just to warm my hands up enough to type!). When it's been c. 30 degrees outside recently, it's up to a balmy 20 degrees indoors and just nice. When friends who have been getting increasingly fractious through lack of sleep because they're too hot stay here they sleep soundly in our cool, dark, quiet house.

Not sure what your problem is (I know nothing about the insulating qualities of cob so I don't know if our stone walls keep a more steady temperature). I wonder if Ian is onto something and it's to do with sorting out the (presumably now hot air) draughts? We managed to stabilise the temperature somewhat by making a big effort to eradicate draughts including making our own secondary glazing, putting draught excluders around doors, identify poorly pointed stonework etc. We even put sheepswool insulation in the roofspace though the thatch is quite thick. (We're thatched in longstraw and unlike reed, you don't go back to the roof timbers to re-thatch, but take off the top layers and recoat so you end up with quite a thick layer).

There must be other PP thatch owners out there - what's your experience?

 

[Penners]

If a properly thatched house is very cold in winter, I suggest that the chief culprit is probably not the thatch. It's a given that virtually any thatched property will be of period construction, so it's more likely that factors such as draughts, poorly insulated walls, ill-fitting doors and windows, etc. are to blame.

 

[Flyfisher]

I've no experience of thatch but Ushy's and Penners' posts makes perfect sense to me - a well draught-proofed house with a large thermal mass (stone walls) is almost certainly going to significantly slow down any temperature changes between indoors and out. Conversely, a draughty house with little thermal mass (thin-ish wattle and mud/daub walls) is going to offer far less impediment to the external temperature - whether cold or hot.

 

[MdB]

From the other post on thatch, it appears that it important to have a ventilation gap under the thatch. If this is the case, won't this be a very good route for the heat to escape negating the insulation effects of the thatch?

 

[robgil]

you could be right Mdb , providing there was a flow of air to carry the heat away. if i were to fit boards to this house i would almpost certianly take the opertunity to fit something like this as well.

http://www.insulation-actis.com/home.php?p=3&l=3

i think the problem with my house is draughts and no central heating , and above all we are only occupying the first floor which will be the hottest part of the house anyway as its directly under the thatch. with very little window space up here it can get very warm. during the winter i used one small electric heater and i was very surprised at how well the heat stayed in the room , until i switched the heater off that is. when the heater was switched off i was witness to a temperature drop that happened so fast time itself slowed down to witness it.

 

[Louis Henry]

I'm a bit late coming in on this thread, but my experience is that the old part of my thatched stone cottage is cosy in winter and cool in summer but the new extension, also thatched, is the opposite. I think in the old roof the narrow gap between the thatch and the lath and plaster (sloped) ceiling has completely filled up with bits of straw, so no ventilation and no cold draughts. The new bit has a smooth plasterboard ceiling so the little bits don't build up, so under my 18" of nicely insulating thatch I have a howling wintry gale. As I understand it over-rafter insulation forms a warm roof construction and doesn't need ventilation, though it should have a vapour barrier under the insulation to stop warm moist air condensing halfway through the insulation. I am intending blocking the gaps at the eaves of the new thatch and filling the slopey section with loose fill warmcel insulation but I would appreciate other people's views on this. Certainly it would not feel right to put an impermeable membrane under the thatch, which would be normal practice with modern insulating material. Thick stone walls are good - it takes the house three weeks to heat up and three weeks to cool down.

 

[Penners]

it would not feel right to put an impermeable membrane under the thatch, which would be normal practice with modern insulating material.

I doubt that an impermeable (to air) membrane would ever be used, nowadays. Where membranes are used, they're invariably breathable, such as Tyvek.

But as I said above, I strongly suspect that a cold thatched building has other problems that are causing the coldness - gaps, draughts, poorly fitting windows and so on.

 

[robgil]

my house is so draughty when we had bees nesting in our roof they were coming through the walls into our bedroom.