underfloor insulation - 3 scenarios - one house?

[paolow]

Hi all,

Well, it seems like the thread I started has been wondrously prophetic. The noth east wind hits my house at the perfect angle to get straight into the cellar and from there up through the floor and also into the cupboard under the stairs where it just sucks the heat out. If it hit the front the problem would just not exist!

I can leave for work and by midday the house is down to 9 degrees - its absolutely freezing.

I very much like the look of the recycled plastic insulation for under the hall / lounge - so thanks for that. I suppose the decision remains as to how to fix it - but thats a minor point.

I really am still very against any kind of glass fibres under the floor so this could well be a winner. Id look to fully pack the space between the joists which are 150mm / 6" so that will make it MUCH warmer.

As for in the cellar? I am not 100% sure yet - but there are types of 'bubble type' foil backed insulation that looks a winner that would be stapled in place between the joists which would still allow the services room. If the 'wool' type insulation is very successful I may yet do this here also. The gaps in the floorboards look innocuous but they add up to pretty much a full board missing in the room which is just atrocious - not to mention the lost heat through the boards themselves.

So why havent I done it yet? Are you joking! Its utterly freezing down there! I'm going to write this winter off and pay a bigger gas bill and head down when I can feel my fingers after 10 minuntes....
It will take some time to get the job right also - and by then this chill will have passed.

But thanks for all the suggestions - and that includes using the membrane to hold up the insulation. I can well see the appeal with chicken wire vs my fingers!

[Peanut Gallery]

If you are getting a draft up between your boards, have you seen a recent post in the 5 years and counting thread, where there is a bead of stuff he and young daughter are pushing between the boards?

[Equus]

Cloudy22 said:

You need think about vapour tightness and breathability otherwise your joists will rot.

This VERY MUCH SO on a Victorian house: and sheep's wool won't save you. Most Victorian properties have issues with inadequate underfloor ventilation to start off with, and adding any form of insulation between the joists will worsen the problem.

Beyond draught-sealing the floor, I'd personally be very wary indeed of adding underfloor insulation in this age of property - I'd rather spend a bit more on my heating bills than store up problems with damp and potentially end up having to replace floors.

[Gooose]

Couldn’t he put 4 inches of kingspan direct underneath the joists and ventilate into the house instead?, he would have to uncover all floors and have a bare wood floor?

[Equus]

Gooose said:

Couldn’t he put 4 inches of kingspan direct underneath the joists and ventilate into the house instead?, he would have to uncover all floors and have a bare wood floor?

Possibly, if there's space to do it for access and without blocking ventilation. Could be easier said than done making it airtight, with all the sleeper walls, though.

[was8v]

I laid 10 / 20mm XPS sheets (get them on eBay) under laminate at my sisters house with suspended floor.

These are made for going under the underfloor heating pipes, but also perfect for cheap, high insulation laminate underlay.

Much quicker then crawling around underneath, but if you are up for that then cheap loft insulation + weed membrane + staple gun sounds good.

I did the same at my house with an old uninsulated concrete slab, made a massive difference.

[paolow]

Thanks for the continuing input guys.

In answer to some questions:

Peanut - I believe I know what you are speaking of - though for such a large area it is NOT cheap. I can insulate 150mm under the lot for the same price - and at the back of my mind is still the issue that the wooden boards are not great insulators

Equus - The problem is that with the insulation being so bad is that I am effectively trying to heat the entire planet (and I am losing). Even with the heating going full blast I can barely scrape 14-15 degrees and the gas bill is already £1200 a year so I know the rads are adequate - though my insulation is not. I am very wary of creating problems but it is quite apparent that the cellar/crawlspace is all to well ventilated.
For info when we moved in we ripped up a layer of laminate and a layer of hardboard from the whole that must have been in place many decades. The only rot evident in the whole floor was by the front door which had clearly been leaking (or the previous owners dogs had) for many years. The air bricks are in place (bar one which I am working on) so I think I will be ok. The house is very elevated with a direct view of the sea so it can get very windy!

Goose - yes I could - but getting the boards into the area in a good enough condition to be useful would be a challenge. It would do for the lounge / hall - but no good for the cellar. Interesting though - though as others have suggested troublesome to seal.

Was8V - interesting - Ill look - It wont do for what I am planning - but could prove useful in the (to be installed) downstairs toilet so thanks. its quite apparent that the current area under the stairs is HORRENDOUS for cold so this will need special attention to make it usable. Fortunately I planned ahead so tapping into the heating circuit will be easy (ish) also to add rad here which I think will be necessary.

To explain the problem a little more the house is very bright and open (unusual for such a style) but the cost is the free air movement.
What I think is happening is that the cold air is coming through the floor and scooting downstairs into the kitchen while the heat from there and the lounge /diner is making its way upstairs. This makes the kitchen in particular an abysmal cold sink and the whole lower hallway is just terrible with the heat loss to the cupboard under the stairs.
From 18 deg with the right wind we can lose a degree every ten minutes for an hour at which point it starts to stabilise when the heating shuts off. Thats too much to bear.

[turbospud]

hobbiniho1 said:

if you do decide to use glasswool i would recommend using knauf loftroll its not itchy like the old glasswool and sheepswool is about 3 times as expensive, i would also use a breathable building paper to hold it up rather than chickenwire in the celler if you are going to be using that area

what he says,the newer building papers are breathable and can be got with foil which can reflect heat/cold but the most important thing is airtightness is achievable depending on how well its installed,
effectively a timber kit wall under your feet