I was wanting to gleam opinion on whether or not people thought it was a) a good idea and b) a cost effective idea to insulate between joists in the subfloor crawl space? In amidst re-doing our front room one job has led to another and to another. Essentially carpet is up, I have cut some holes in the floor (to be carpeted) and now spend my evenings underground. We live in a 1900's sand stone house with solid walls. Rooms are all lathe and plaster with no internal insulation. It can get a little chilly from time to time hence the current job of beefing up the heating system. Whilst underground I wondered that whilst I have access should i insulate between the floor joists? The subfloor crawl space is well ventilated with a number of external vents- so noticeably so you get a nice draft out of the holes I am about to put electrical back-boxes in. No noticeable damp. Here is what I am dealing with Ignore the half finished piping and the strips of carpet to make things a bit more homely whilst down there. Joists are 160mm deep. Access for the most part is good- few areas towards the edges of the room which are tight and a small area under the bay which I cannot get easy access to. Would filling with insulation likely make a noticeable difference to offset the cost and time to install? I wouldn't have thought damp would be an issue as the joists would still be exposed. I guess celotex would be the ideal choice but with the area needed to cover (room 1 -6.5x5m and room 2- 4x5m) it is going to cost a fortune and I will be limited by the lengths i can squeeze thought the holes in the floor. I had thought about filling with earthwool (have loads of it in the shed- 170mm) but then retaining it will be a pain. I had thought about putting lots of small screws along the joists and then criss crossing some twine to retain it or is there an easier off the shelf answer?
Use flexible insulation slabs, can be held in place by netting, tile batten or or cord nailed to joists to support it. https://www.insulationsuperstore.co...m2-pack.html?gclid=CNfLuJC8lNICFeq87QodmnUFog Knauf insulation earthwool flexible slabs, is another suitable one, again variable thicknesses available.
Thanks for the replies. Cutting accurate blocks of celotex fills me with dread! Is the advantage to the insulation slabs just that they will be easier to keep in the gap when compared to roll insulation? Has rockwool improved over the years or is it still the most uncomfortable substance known to man no matter how many layers and masks you use? I had thought of just cutting the 170mm roll whilst in the wrap with a hand saw just slightly larger than the gap and transporting it underneath all still wrapped. unrolling it underneath I had hoped I could unroll as you would do a loft - just do it upside down fastening as I went. In theory I thought this might work but in practice with limited space I can quite conceivably see me with earthwool on my face.
I can tell you that cutting Celotex is a bl**dy tough job due to the accuracy and multiple cuts involved, I wouldn't go down that route and I speak from experience. Not sure what the slabs are like but I fitted Knuaf Earthwool in my loft, the 100m loft stuff on a roll, and it was fine, didn't wear a face mask at all. You might need some protection if its above your face, but no where near as bad as the old fibreglass stuff.
Cutting and measuring Celotex is actually very easy Measuring use a "story stick" - its just a piece of scrap timber, that you offer up to what you want to measure and mark the widths,lengths etc. Cutting - Circular saw with an old thin blade, battery ones are the best. Just lay the insulation down on some battens and run the circular saw through the insulation using a straight edge to keep it on the mark. Any gaps, just seal down the side with expanding foam. To temporarily hold the insulation in place under the floor - hammer some plasterboard nails part way in. Then when you offer the insulation up just push it in a little and the nails will hold it in place. Ideally you want the insulation close to the floor rather than the bottom of the joists. Remember to insulate the pipes and always a good idea whilst you are down there to spray for rot/worm etc.
Pipes will be insulated- they are not even soldered yet. Just cutting lengths and working out runs to get round joists/obstacles. What do you recommend for wood treatment? I have previously used blackjack paint on stuff but with would take me weeks to paint everything under there and I would be covered. is there a spray version?
Well, yes it is and no it isn't...it is easy to do but takes a lot of time and is very messy. And measuring under the floor, having to cut pieces small enough to get down there (which means more pieces to cut) will be very laborious. If it were me doing it, I'd be looking at an "easier" option like the insulation slabs.
There is no easy way to insulate that sub floor that I can think of. In any case, it'll only make a marginal difference anyways - your real issue is draughts. If you can afford to lose 8mm from the top - ie add an extra 8mm without it affecting door opening clearances, etc - then what I have done in the past is to used low density fibreboards which are used as laminate underlay. I got mine from Wickes and they came in sheets which were around 4' x 2' size, I think. I lay them over the floorboards, ran a bead of cheapo frame sealant where they butted together and also sealed then against the walls. Draught proof floor with a useful extra level of insulation too - dead cheap and dead easy to do. Wooden floorboards are already quite nicely insulated, and the floors are the least of the heat retaining areas in a hoosie. So something as simple as I suggest will be enough - spend more effort on external walls and ceilings . And if you do want to bother spraying the joists below - although if they are bone dry you shouldn't have an issue anyway - then Everbuild Lumberjack which comes in 25 litre tubs is great stuff and as nice to use as anything like this can be (water-based, use a pump-up garden sprayer and wear a mask). But, hardly necessary.
I was hoping most of the draughts will be mitigated by good quality and well fitting underlay and carpet- ordered but in storage as it has taken so long for me to finish the room. As you say I think the wood will be ok- it is all nice and dry. no evidence i can see to suggest woodworm. We are going to be in this house for the long term so was hoping the outlay at present will eventually be offset. Think I am going to try pick up some battens and see how easy the eathwool I have is to put up. if it is a nightmare i will be going for the block insulation and save the rest of the current insulation for the loft space.
Highly recommend Everbuild Lumberjack Triple action wood treatment from TS & use it in a garden sprayer. http://www.everbuild.co.uk/Triple-Action-Wood-Treatment Shame 22mm pipe not clipped.
Not clipped at the moment but held each side just out of shot with some twisted copper wire- haven't soldered yet and last time I pre clipped it melted the nearest clip...lesson learned!
Damp rag or two around pipe & clip, problem solved. And the Earthwool is specifically designed for installation by friction fitting.
that was with a rag (only 1 mind you) and heat mat...had 4 22mm joins next to each other and although local solders were ok the plastic was not
You can use slip joint pliers clamped to pipe to absorb the excess heat & stop it traveling along pipe. inconjunction with rags.
Cool- thanks for the tip. I assume pliers are also wrapped in damp rags or same result will happen with the plastic handles?
I don't find the heat travels that far up the handles which have no rubber grips,the slipjoints are basically a heatsink, but I use a mapp torch,which I find quicker, so the fittings don't get the chance to get really hot, you can still wrap a damp rag around yours, copper transfer heat very easily.
Using MAPP too...but i'm a novice to plumbing so maybe i fried the joint a wee bit! Had a couple (including the melted clip issue)that I just couldn't get to take- the solder just beaded up and ran off rather than being sucked in with the flux. I had been keeping my flux brush (paint brush- cut to size) in the pot (several weeks)and after several joints failing in the same sitting (no probs before) i used a new brush and all was good. Not sure if the flux over time had disolved the bristles a bit and was leaving some residue. Anyway i now don't keep the brush in the pot now and all is good.
Forums
Facebook
Twitter
You Tube
Instagram
Shop