Hello!
I have really enjoyed reading the posts here, and am now seeking some guidance with a question of my own...
My house is semidetached with the standard layout of front and back receptions (now one room), hallway running through the middle adjacent to party wall, and kitchen at the back. The reception room has a suspended floor, abutting the solid floors of the hallway and kitchen. The two outside walls of the reception room, which are at right angles to one another, have four air bricks along the side, one at the front. The air brick in the wall at the back which would have created a cross draught has become part of an internal space when the kitchen was extended to the full width of the house at some point.
The reception room floor is beautifully finished in engineered oak, and sadly uninsulated. The tops of the air bricks are slightly higher than floor level, and plenty of air gets through above the floor in spite of my attempts at sealing. My question is: would it be feasible to block up the air bricks and install some kind of mechanical and controllable ventilation under the suspended floor to make the conditions more comfortable? I know a piecemeal approach not ideal, but I don't have the resources to do huge amounts of work. I would also like to switch away from gas central heating and I understand that air source heating doesn't work too well unless house is well-sealed so it would help with that too.
Thanks for reading :-)

If you are thinking about filling the underfloor void, then using lightweight expanded recycled glass beads which are free-flowing and non-combustible, with a constant insulation value (unlike eps that reduces over time), they do not take on quantities of water (unlike vermiculite) and have a good lamda value might be an answer?

EPS has a theoretical constant U value but has higher compressibility if performing any structural function and we can testify is prone to rodent, bird and particularly insect attack as we have ants' nests in the polystyrene insulation of our caravan. We take some information from the US Department of Energy :-(https://www.energy.gov/energysaver/weatherize/insulation/insulation-materials)

@Petlyn, your link refers to the degradation of XPS, not EPS. XPS is known to lose R value over time, EPS is not, and the same goes for structural functions, where XPS is used and not EPS.

@djh, I am glad to hear I am not the only one with EPS sitting in my garden for years. Birds seem to like pecking at it, our chickens find it irresistible. Not good for them or the EPS so I had to block them from getting to it.

Petlyn, do you have any idea whether beads could be blown in using the air brick points (or holes made on same level) for access, thereby avoiding the disruption of lifting the floor?

Posted By: NanuchkaAm I understanding correctly that a bead fill means venting not required? Probably being dumb, but could you explain how?

It's is quite simple really, an under floor void needs ventilation. If you fill the void then there is no void so nothing to ventilate.
The problem with blowing in beads (usually EPS beads) is that it is difficult to ensure a full fill. If you get a partial fill then you still have voids - which need ventilation.
From your description above regarding the air brick location and the solid floor - the reading to me sounds like you might have a dead air space in one corner (no cross flow) that may or may not cause problems in the future

Posted By: NanuchkaTo answer, the middles (horizontally) of the airbricks are about level with the top of the floorboards. The connecting holes twixt outside and subfloor space are roughly angled downwards, but I do mean roughly! The only thing between the holes and the living space is skirting board. Builders were as clueless as I when it was being done and time pressure meant I didn't have a chance to research. I wish now I'd put my foot down and made them work on a better solution.

When was the work done? Can you get the builders back to do the job properly? Does the ground level outside allow the airbricks to be placed in the correct place?

Posted By: NanuchkaI would also like to switch away from gas central heating and I understand that air source heating doesn't work too well unless house is well-sealed so it would help with that too.

Air source heat pumps should work as well as gas CH in a house that is not too well sealed - it's just that it will be expensive to install because you will need a bigger unit and expensive to run because the heat will be leaking out. But then the same will apply to gas CH. If you have got gas CH why swap to air source heat pump? - Do you mean air to water or air to air? If it is air to water then the heat emmiters (rads or UFH) will need to be sized to account for the lower temps of an air to water system. If it's air to air - how will you duct the air around the house, or do you plan individual units in each air space?

Tony thanks, that's good to know.

The beads can be blown up to 2m to fill a dead space because the air will exhaust back towards the airbrick over the beads and eventually the beads will form a drift up to the underside of the floor; introducing more beads will bring the filled void back towards the blower. If the distance for the blower is too great, (say 2m) then as the beads are free-flowing and could easily be poured through a 3 inch hole cut into a floorboard which can be plugged afterwards.

The easiest course might be to cut a hole inside the house close to the wall above the airbrick, with one person pouring the beads through the floor and another directing the beads with a light from outside through the airbrick?

What sort of area and depth are you looking to fill?

Oh, and depth approx 0.4m from memory.
Once fill complete, can the air bricks then be completely sealed?

Tony I saw the thread where you were talking about trying EPS fill - did you? Do you or anyone else know where I can get more info both on the science and the application? I would need to find someone to do it for me, quite possibly impossible to find anyone who's done it before in Cornwall, would be good to have as much info as possible...

The voids between the beads are too small to count as voids.

I can help in February to fill void.

I know of a load of floor voids filled with eps beads across the seas over 5 years ago with no problems.

I have applied for grants to trial this in a test bed house, didn’t get the funding though should have.

Hi Anna, we pumped a lot of underfloor voids with EPS and closed the vents over 10 years ago, I had no call backs so 100% sccess, I even did my own house. I don't have any commercial involvement in EPS but it is cheaper and has a better Lambda value than Glass Beads which would probably also work well. We don't do much renovations anymore as we're now building Off-Grid Developments.

Is pumping underfloor voids diy'able? What kit would be needed?

Not afraid of DIY, quite capable of all sorts, have access to core drills and know how to use them etc.

8m x 7m with 0.4m depth so around 23m^2 unless my math is off

Thank you. No need yet, just gauging viability. Gotta pull some more boards up first and investigate the wiring/piping situation and if there is enough room for access... Could do with moving a couple of rads and want to add some sockets in certain spots. Guess with EPS I also need to protect the cables?

Suspended wooden floor 1970's ish build. Cavity walls done, double glazing done, loft insulation now 18 inches.. But the floor still feels cold and on a windy day you can feel a slight floor breeze :/ Guessing its that.

Did consider pulling carpets and putting down some vapour permeable air impermeable membrane on the floorboards then the usual underlay and carpet on top. Not sure if a good idea.

Got a compressor and know how to use it, and lifting boards and pouring first sounds like a no brainer.. Punch nails through?
Guess you need to fill to the brim? dont want floor - beads - void - floorboards?

Early days of formulating a plan. :)

Thanks again,
Sam

Okay, thats useful to know.
Just on external walls or all walls (guessing all walls)?

Sometimes its hard to know what the solution for various problems are, so much appreciated.

Will probably start my own 'home improvement' thread once I have my thoughts straight. :)