Subfloor ventilation

[delbs]

Have moved into a split level house in northern NSW coast near Coffs Harbour.

I need to improve subfloor ventilation, it’s approx 30yr old house. It’s on a sloped block with a pool. In the pool yard which is ground level I can see multiple (16 from memory) weeper holes on a double brick wall that flow underneath the house.

On the opposite wall which is the garage and internal house walls I don’t have any vents so a slow leak from a pipe has made some dirt damp and I can’t see anywhere it has the chance to dry out

Question is, for me to punch a hole through and allow passive airflow through it needs to be an internal wall. Are the brick grid/vents I see online and Bunnings etc suitable to use inside or will I likely need an active powered fan solution to push the air through to another external wall and not inside?

Just asking for a perspective based on others experience before I get the bias opinion of a ventilation company over to take a look

Cheers
Nathan

[Beardy]

Google underfloor ventilation fans, I can’t remember the company but they sell a fan designed for continuous running that uses very little power, they also have some helpful tips on their website
If fitting or replacing vents the best ones have the bronze mesh inserts rather than the terracotta ones as you get twice the airflow from the equivalent size

[rwbuild]

What Beardy said

[delbs]

Ok thanks for this

So I can see kits that are sold on a per sqm basis and they don’t seem too bad. I’d have to get the sparky in to wire it up for me unless the fans come pre wires. Is this something that you have done yourself? Ie aside from the electrical side of install is there a need to go through a business? Installled by a local business for a 4 beddy house is around 4.5k

Is there that much of an art to selecting the points to install that I couldn’t figure out myself with the help of forumites?

Cheers
Nathan

[Beardy]

There is no reason you can’t do this yourself but need to understand what you are trying to accomplish with appropriate vent location. If you do some more online research you should be able to get a handle on it. The fans are likely to have a plug lead on them so will need to get a powerpoint installed

[delbs]

Yeah agreed. I think finding vent intakes is ok but is it a 2 to 1 ratio of intake vs exhaust? For a 4 bedroom house in a coastal area it seems 4 intakes and possibly two exhaust is adequate. Do the exhausts all have to be on external walls?

I’d expect if an exhaust would be on an internal wall it would bring a smell of wet dirt or something into the house assuming the fan doesn’t do anything other than just pull air through than actually filter it

Cheers
Nathan

[rwbuild]

ALWAYS vent externally, the spores in sub floor damp can be a real health hazard to anyone with a respiratory problem especially in young children or aged people

[delbs]

Agreed but where my weeper holes are at ground level to cross over the other side of the house are no direct access to external walls. Split level design means I have downstairs bedrooms and garage lower than the under house ground where the weepers draw into. so as much as I want to try cheapest passive option first by just installing grills knocking out bricks i think a fan forced option must be the only way to redirect air flow. I’ll keep reading up on this

[rwbuild]

Can you post a rough sketch of the layout just showing the room/garage area and the subfloor area

[delbs]

Can you post a rough sketch of the layout just showing the room/garage area and the subfloor area

Alright lets see how we go with this. Heres a quick snapshot of the front of my place

The green square represents a double brick wall facing the pool yard. It has 4 sets of 4 weeper holes going into the brick cavity which leads to underneath the house represented by the red rectangle

Then the blue rectangles represent the internal wall where the subfloor finishes and then the garage and lowerlevel slab begins. Then the blue rectangle on the far left is the external wall of the house obviously.

There is a rear pergola at the back of the house with brick paving same as pool yard but its filled and bricked off from underneath i cant get access into it.

The front verandah however is a floating slab as ive verified the gutters and other things under there a few times so my thoughts would be an active vent/fan solution may be able to dig through and install a vent at ground level under the floating slab at front of house perhaps.


subfloor-pic.png

Another top down perspective shows the green weeper holes and red underfloor and verandah and internal and external blue walls.

subfloor-pic2.png

Just wondering if anyone else has tackled a similar split level design and whether installing the passive brick vents worked over time. i cant see how a passive brick vent could be installed that would have natural flow but hoping there is a way as its the cheaper first step i can take myself.

Happy to hear any suggestions good bad or otherwise

Thanks
Nathan

[rwbuild]

Vent.pdf
See attached

[delbs]

Vent.pdf
See attached

Can’t open that sorry mate. I’ll give it a shot on the computer.

[crowie]

I've had one of these running 24/7 under my house this past 3yrs if that's any assistance.....

TT PRO Mixflow Inline Fan 200mm - Fanco

[delbs]

Vent.pdf
See attached

Thanks for making this Rwbuild, so your suggestion is for the ingress / egress vents to be at the front of the house coming out from under the from verandah which is a floating slab? a Fan solution or just vents to begin with?

Cheers,
Nathan

[rwbuild]

Yes, from front of house and a fan on each duct, unless you keep circulating the air in the dead zone, you will always have a problem