How to ‘finish’ a concrete floor in cellar?

[ThornhillMike]

That's a large space to ventilate. The key is to experiment in terms of what system is required. To get decent air quality for use as habitable space you want 4-6 air turn overs per hour. Assuming your basement is 2m high thats 400 m^3 of air so you likely need extraction rates at least around 1200 m^3 per hour. I use Tornado dmevs but none of them would give close to that. I would imagine some in-line fan designs might deliver that. It also depends on your set up down there. If there are things like 90 degree turns then you may need fans on internal walls between rooms to help ventilate the air through the space better.

With a large space like that I would personally install some more air bricks - the larger the better (https://www.castironairbricks.co.uk/). I think standard single air bricks would be too small to ventilate that space. Put some high extraction rate fans in the back and see what sort of air quality that gives.

As @a twig points out my air volume is indeed c200m3. Think four square rooms with a central hallway; no direct "line of flow" bit enough space I think to be able to draw air sufficiently. I am still curious if the artificial air flow creates any sense of noticeable 'draught' in your setup...

 

[Stevers]

If the basement has a bit of heat and a clear chimney flue, that might be enough to ventilate the area.

I can suggest this because when up on my roof I was most impressed by the vicious blast of warm centrally heated air coming out of the chimney flue for my living room. I took this to be a bad thing in the context of a cosy living room and did something about it. Initially this was via a succession of 'balloons', but I have now settled on putting a 'sheep' up there. It's a 35' draw and my open fires are smoke free internally - as Iong as I remove the 'sheep'.

Chimneys play a part in ventilating old houses and can be very effective once they get going.

 

[NecessaryWing]

1200m3 per hour is a lot, we are talking units like this typically used in commercial premises and requiring a 12” diameter hole in the wall, are you sure about your sums?

I think Mike’s post already had the volume at 200 cubic meters

Ah sorry! I thought op meant the cellar was 200 sqr mtrs (area). So 600 m³/hr of extraction would give 3 air turnovers per hour so two 300m³/hr fans - I don’t know if dMEVs go that high. Even with the same ventilation basements vary considerably from place to place so you may get success with less than 3 turnovers per hour. Whatever gives you around 60% RH or less and less than 100Bq/m³ for radon - these are the two main air quality measures for a habitable space down there.

Placing fans strategically is advisable. I have mine opposite the doorways which are open arches (no doors).

Yes - you can feel a breeze through the cellar but I wouldn’t say it is overly strong unless you’re standing near the air bricks. I get a strong breeze near the boiler intake vent but that’s an 8 inch vent.

 

[ThornhillMike]

If the basement has a bit of heat and a clear chimney flue, that might be enough to ventilate the area.

I can suggest this because when up on my roof I was most impressed by the vicious blast of warm centrally heated air coming out of the chimney flue for my living room. I took this to be a bad thing in the context of a cosy living room and did something about it. Initially this was via a succession of 'balloons', but I have now settled on putting a 'sheep' up there. It's a 35' draw and my open fires are smoke free internally - as Iong as I remove the 'sheep'.

Chimneys play a part in ventilating old houses and can be very effective once they get going.

The basement is on the CH circuit so warmth is not an issue. There are also three fireplaces down there so they may well act in the positive way you say; thanks

 

[ThornhillMike]

Ah sorry! I thought op meant the cellar was 200 sqr mtrs (area). So 600 m³/hr of extraction would give 3 air turnovers per hour so two 300m³/hr fans - I don’t know if dMEVs go that high. Even with the same ventilation basements vary considerably from place to place so you may get success with less than 3 turnovers per hour. Whatever gives you around 60% RH or less and less than 100Bq/m³ for radon - these are the two main air quality measures for a habitable space down there.

Placing fans strategically is advisable. I have mine opposite the doorways which are open arches (no doors).

Yes - you can feel a breeze through the cellar but I wouldn’t say it is overly strong unless you’re standing near the air bricks. I get a strong breeze near the boiler intake vent but that’s an 8 inch vent.

Thanks. I'll monitor the RH and see if there are any pockets of 'stale' air.

 

[Stevers]

The basement is on the CH circuit so warmth is not an issue. There are also three fireplaces down there so they may well act in the positive way you say; thanks

Both of our bathrooms (ground and first floor) have the Passivent system with humidistat grills vented through internal ducting to the roof that is insulated only through the loft. These require no electrickery, are extremely effective, but as far as I can tell are no longer available. They were the very latest thing when we did the initial restoration of the house in 1997. Naturally they gather dust and cobwebs but the only maintenance required is a brush with a hoover every couple of years. An insulated lined flue from one of those fireplaces could work wonders in terms of 'natural' air extraction - if they're not warm enough to do the job already.