There are many threads about insulating a suspended floor, and with only a small ccawl space, means lifting nearly all the good T&G boards to install.
That is a big job, disruptive to skirtings etc, and with potential 25% board loss, means the floor will never be the same again.

I know that the phenolic spray insulation for attics / roofs is flawed, and often damaging, but does the logics apply to underfloor voids too?

Q-bot seems to be some university robot & AI project that is starting to be commercialised, so its new ....
Link:
https://www.q-bot.co/service.html

Its a robot that goes into the sub floor void, and sprays Phenolic / PIR insulation ALL OVER the joists and floor boards from underneath.
It seals all the gaps, makes them air tight, while still retaining the all important air flow underneith.

I am fully awair that sprey chemical foam insulation has been mis sold as a (bad) solution for roof insulation, and has caused many serious and exensive issues.
BUT - the very reasons why spray foam insulation is bad for a roof, may actually be very appropriate for a floor.
Roofs are VERY expensive. They are inaccessable, and need to deal with a shit lot of extremes from both inside and out.
Work on them is expensive because they are ...... inacsessible to nearly everyone.
They are also 'out of sight, so out of mind'
Damage can be slowely happeneing for ages without notice, and then .... its a REALLY big deal.

Floors on the other hand, are mostly exposed to a fairly steady and constant regeme, and and issues are noticable pretty quite (by me at least)
AND - if bad things do happen, anyone can get at them, and .... while a nusance, it is not 'catastrophic' - its just work, that even a DIY'er can do.

OK, the spray robot is not cheap ... but it is quick, and .... deals with the detailing, coz it just sprays its chemical foamy stuff all over everything, so not gaps, or cold bridges or whatever.

BUT - lifting the floorboards, has got to be a labour of love, its a lot of hours, and many opportunities to get the micro detailing wrong .... and end up with a soggy joist a few years later.

No sales people, - I just came across them, its a spin off from some university research project, that hasen't been commercialissed yet ... as I understand it ....

They don't claim anything, they have a website, and .... whatever.

Anyhow, when asked, they suggest:

"We normally apply 125mm of insulation, resulting in a post U-Value of <=0.25 W/m2/K (depending on void conditions). The results across 100 homes show an average post-installation of 0.19 W/m2/K, representing a 79% improvement compared to before."

I know that paying for underfloor insulation is unlikely to ever 'pay off' - but I do want to try my best, and the floor boards and especially skirting boards are really deep and beautiful, and I really don't want to trash them.

Here is a video link:
Q-Bot, robotic device lowers insulation costs | 2018 Ashden Award

Any thoughts?
Thanks
Phil

It doesn’t work, real subfloor have too may probs, junk, wires and pipes, uneven, sleeper walls etc

From inside or from outside and what about the cavity?

Has a full fill with EPS beads gone out of favour - or is the crawl space too deep (= too much volume (expense))

Posted By: tonyFrom inside or from outside and what about the cavity?

from inside:
per another place (...):

seal up all existing ventilation grilles save one, and force a small quantity of house-air into the void (1 cfm per 50 square foot of area), thus creating a conditioned crawlspace.

Requires a very small extraction fan on the remaining vent...

The makeup air entering the crawl space is conditioned air from the house upstairs; since this conditioned air is drier than outdoor air, it doesn't lead to condensation problems.

(also expels any radon that might be around...).


FWIW,

gg

Err, not usually. Interior air is usually more humid than exterior air in a heating climate.

djh, do you really believe that ? !

https://appoloheating.com/blog/air-house-drier-winter/

gg

thanks for the comments, I cannot 'insulate' my walls / foundations as mid terrace.

Removing / ripping up TnG flooring is a major task, and managing the detailing on dwarf walls, and where joists rest on / in walls is near impossible detailing to get right even then.
BUT - what is the purpose of venting the sub floor? - Is it to ensure that the joists get ventilated? - if so, then surely ANY insulation negates this ability for the exposed timbers to be ventilated.

YES, the void is full of junk. bricks, pipes n wires etc.
I could crawl round to collect / move, but definitely not enuf space to apply insulation from under, unless you are a robot .....

My local housing association have signed up for it.... but that doesn't mean it is a good ideas.

What might hypothetical problems, be?

The easy alternative is to not insulate the floors..... which also has a cost ....

e.g. see this article:

https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces

(... its east coast US centric, but largely applies to UK too, although some of the problems are a bit less extreme in the UK - depending on location within the UK).