insulating under suspended timber floor

[abr]

Hi
We are in the midst of insulating between the joists our timber floor in our 1930's house.

We have lifted the floorboards and have fitted a breather membrane over and between the joists that is supporting 100ml earthwool blanket insulation.There is a very good air flow from the air brick and a good amount of space underneath.

The joists run parallel to the external wall and at right angles to the internal walls. However there is a gap of between 1-2 inches between the end of the joist and the brick internal wall.

We intend to put a VCL over the top, adhere to the walls and then replace our original square edged boards. We will silicon gaps.


My question is do we fill the gaps at the end of the joists with insulation? Would it cause the ends of the joists to rot?

Cheers
A

 

[pinenot]

It certainly won't cause condensation if you use earthwool to fill the gaps, it allows a certain amount of breathing

 

[abr]

It certainly won't cause condensation if you use earthwool to fill the gaps, it allows a certain amount of breathing

Brill! Thanks

Another question- we need to adhere the VCL to the walls a little way up way up from the floor behind the skirting. What can we use?

Cheers

A

 

[pinenot]

By adhere I expect you mean glue/stick it, but when you think of it, that means you will be effectively closing the vapor controlability?

 

[abr]

Hi

That is correct. The vapour barrier will be the top layer in the sandwich to achieve airtightness. Vapour will be able to escape downwards via the breathable membrane and air brick but will be unable to escape upwards through gaps in the floorboards into the room.

In this senario, is it still Ok to put earthwool between end of joists and wall?
How do I fix the vapour barrier to the wall to achieve airtightness?

Cheers
A

 

[freddiemercurystwin]

You don't, you apply a sealant between the skirting and boards if you really think it'll help. A VB is overkill in this situation IMO anyway. Especially when you've only used a bit of mineral wool.

 

[pinenot]

I concur, a vb in this instance is not a gain, merely an extra cost.
Getting the floor -floor/wall joint airtight is the important thing here. I copied in some informative reading for you - http://www.superhomes.org.uk/resources/draught-proofing/#more-14248

Cheers...pinenot

 

[abr]

Hi
Thanks for the advice. I am always interested in advice from experts and especially solutions that save money.

The problem is that it is nearly impossible to seal up all the cracks between the original square edged floor boards. We tried this over the winter and despite numerous tubes of sealer we were still freezing even at 21C room temp. We had to sit with blankets around our ankles because of the cold draughts coming from the floor. We swore that we would not spend another winter like it. We do not wish to use carpet as our boards look lovely.

I was following the case study of how to insulate suspended floors in:

http://cambridgecarbonfootprint.org/under-floor-insulation/ and
http://www.cse.org.uk/downloads/file/warmer_bath_june2011.pdf

In Cambs they used a polythene sheet as a vapour barrier. I had thought a VB would, properly sealed to the wall, eliminate all draughts as we are unable to seal the breather membrane to the wall all the way around the edge of the room but would be able to do so with a VB that is laid flat and not draped between joists


Any further thoughts?

Cheers

A

 

[pinenot]

Just had a new lounge carpet fitted and had exactly the same problem, luckily I have white painted skirtings, so I taped every joint inclusive floor to skirting, with masking tape. Painted the skirtings and masking tape (can't see the tape joint) a good underlay was laid and the carpet fitted with smooth edge, result no drafts chilled legs a thing of the past (noticeable overnight) - try it it works...pinenot

 

[abr]

Hi
Thanks its really horrible to have cold ankles.

The problem is that I really do not like carpet plus advised not to have it by my consultant because of allergies. We have to have hard surfaces that can be disinfected. Hence will stick with original floor boards for the moment but may have a new floating floor on top at some point in future when funds allow.

The question now is to VB or not to VB?

Cheers
A

 

[jagillham]

Some recent research showed that carpet can be better for allergies, as they hold the allergens rather than hard flooring where they remain airborne. Might be worth considering?

 

[abr]

Hi
Thanks for the advice. I am always interested in advice from experts and especially solutions that save money.

The problem is that it is nearly impossible to seal up all the cracks between the original square edged floor boards. We tried this over the winter and despite numerous tubes of sealer we were still freezing even at 21C room temp. We had to sit with blankets around our ankles because of the cold draughts coming from the floor. We swore that we would not spend another winter like it. We do not wish to use carpet as our boards look lovely.

I was following the case study of how to insulate suspended floors in:

http://cambridgecarbonfootprint.org/under-floor-insulation/ and
http://www.cse.org.uk/downloads/file/warmer_bath_june2011.pdf

In Cambs they used a polythene sheet as a vapour barrier. I had thought a VB would, properly sealed to the wall, eliminate all draughts as we are unable to seal the breather membrane to the wall all the way around the edge of the room but would be able to do so with a VB that is laid flat and not draped between joists


Any further thoughts?

Cheers

A

I hate carpet so it is not a option . We will have to make do with our original square edged floor boards. The plan was to have a breather membrane draped over the joists and supporting earthwool between the joists with an airtight membrane(VB) on top sealed to the wall. The gaps in the floor board would be sealed as best we could.

Therefore to VB or not to VB that is the question?

A


Cheers

A

 

[freddiemercurystwin]

Just do it if you want to. But if the insulation is installed correctly then it will serve little purpose. IMO rockwool slung between the joists is not an ideal solution.

 

[dhutch]

Just do it if you want to. But if the insulation is installed correctly then it will serve little purpose. IMO rockwool slung between the joists is not an ideal solution.

Do you have an alternative solution or suggestion?


Daniel

 

[dhutch]

I cannot see why you would not add a airtightness layer while doing this work, to omitt it im my mind would be maddness, in terms of energy loss and room comfort I would have thought its proberbly as important as the inslualtion itself if not more so. Obviously if you are improving airtightness, as some point, you may have to consider air managment, either in the form of the nasty trickle vents, or a MVHR unit but I have been considering the latter even without finishing the airtightness improvments as I feel that the increase the air quality and reduced window condesation, is worth the cost if your going to live there a while.

Im not an expert, as yet I have not done anything to me own house, the front half of which (living room and dinning room) is suspended, conreate at the rear under kitchen, as build in 1940's as state funded housing.

I have laminate flooring, put down by the previous owner, floating on an underlay, which in itself provides a good barrer, however I still get drafts around the edges and around fittings in partiuarly the consumer unit, as the house has been replastered using dot and dab without a solid bead around the boards. Im sure this could be improved, but at the moment, its fairly drafty in winter.


Daniel