Is a cavity necessary?

just do it

I'm living on the western exposed coastline where a partial fill cavity is recommended due to the driving rain. But there is a large amount of these cavities being pumped at the moment, converting the walls to full-fill cavities.

Throw the newer building technologies into the equation and full fill or single leaf wall construction is on the increase.

So the question is, is the partial fill cavity in exposed areas necessary? Opinions welcome

Poor Uncle Tom

It's not necessary, and the watertightness of the outer skin of your build depends more on good detailing and good workmanship as oppesed to the type of construction you choose.

/btw, if a 'cavity' is filled, is it a cavity anymore?

sinnerboy

My dentist says yes

just do it

Poor Uncle Tom wrote: »

It's not necessary, and the watertightness of the outer skin of your build depends more on good detailing and good workmanship as oppesed to the type of construction you choose.

/btw, if a 'cavity' is filled, is it a cavity anymore?

Fair enough PUT, I'll rephrase - Is partial fill still recommended in an exposed location on the Western coast?

Given all the cavities that are being pumped around here, including builders houses, I'm wondering will it become obselete. Why bother with the insulated boards and all the hassle doing that job properly involves, when you can let the brickies lash on and pump the cavity after (ensuring cavity is clean, wall ties are at right angle etc)

sydthebeat

just do it wrote: »

Fair enough PUT, I'll rephrase - Is partial fill still recommended in an exposed location on the Western coast?

Given all the cavities that are being pumped around here, including builders houses, I'm wondering will it become obselete. Why bother with the insulated boards and all the hassle doing that job properly involves, when you can let the brickies lash on and pump the cavity after (ensuring cavity is clean, wall ties are at right angle etc)

i believe partial fill cavity wall has significantly dropped down the list of 'best' construction methods. It has gone from the industy standard of 10 years ago, to being barely able to reach min building regs.
The main issue is with workmanship and the ease at which the performance of the insulation can be negated ie with ill fixed boards, mortar snots, bad detailing leeding to thermal bridges. Even only last year, i inspected a site where the builder had total filled the return from inner leaf to outer, no insulation and no DPC!!
The proof of the pudding is in the ratio of construction methods to passive level low energy builds... the vast majority being EWI and timber frame.

just do it

sydthebeat wrote: »

The proof of the pudding is in the ratio of construction methods to passive level low energy builds... the vast majority being EWI and timber frame.

Yes that's an interesting observation. Of the two I'd favour EWI, but how will it last the test of time I wonder? Any examples of lads going to passive level with wide full fill cavities? Whilst there seems to be plenty near passive, I don't know of any passiv haus level ones yet.

beyondpassive

Tullow, Co Carlow passivhaus with 300mm cavity basalt wall tie, Bead filled on EPS raft, was filmed by RTE's 'About the house' this week. <SNIP> is the Passivhaus consultant. Should be on telly in Autumn


Mod edit: Please stick to the topic

just do it

just do it wrote: »

Yes that's an interesting observation. Of the two I'd favour EWI, but how will it last the test of time I wonder? Any examples of lads going to passive level with wide full fill cavities? Whilst there seems to be plenty near passive, I don't know of any passiv haus level ones yet.

Interesting observation re thermal mass and concrete build vs timber frame passive house. Quote from the occupants of the Denby Dale certified passiv haus in the UK after living in it for 6 months:

"The other interesting thing that we’re noticing is to do with thermal mass of the building. You’d think that when you opened the window the house temperature would go down rapidly – it does while the window is open obviously but as soon as you close the window the heat’s back up again – thanks to the thermal mass inside the house retaining the heat. We’re interested in how our house – built using cavity wall construction – would compare with a timber framed one in terms of temperature changes. We’ve heard that timber frame Passivhaus buildings can have much steeper changes of temperature. If you open the doors here in winter for 20 minutes, it wouldn’t make a difference. Whereas if you did that in a timber frame Passivhaus you could lose the temperature very quickly. This could be a case for heavyweight construction like cavity wall as a way of offering thermal mass as a buffer against rapid temperature changes."

(Mods - remove if need be. I'm reckoning it's ok as Denby Dale has been mentioned plenty on here previously)

I assume EWI would provide the same thermal mass as wide cavity when they both use the same inner block?!