Calculating Purge Ventilation

[Ferdinand]

Up early to work whilst it is a bit cooler, and cool the house by a few degrees for breakfast time, and I am wondering about purge ventilation. Hoping to drop the temp by 3-4 degrees from the 27C it was mainly at last evening.

 

Is there (or has there been) any useful work on the amount of open window needed to cool a house down, or rules of thumb?

 

This morning I have about 200mm x 600mm x 4 area (=.48 sqm) of open skylight (ie 600mm centre hinged open 200mm) upstairs, and a conservatory door open downstairs (=1.5 sqm ish), and it is going to have a noticeable effect. A couple of top windows would not be sufficient.

 

It depends on the ΔT between the inside temperature and the outside temperature, and also the thermal characteristics and size of the house and the materials, decrement delay, thermal emissivity etc, time that it is open etc.

 

Is anyone aware of anything?

 

I am thinking of something as simple as the building regs rules about window area vs floor area for adequate light etc.

 

My 'single data point guestimate' says 0.5-1 sqm of ventilation opening aperture per 100sqm of average storey floor area size should be enough. Probably.

 

Cheers

 

Ferdinand

 

 

Edited August 26, 2019 by Ferdinand

[SteamyTea]

What is the house made from?

 

[ProDave]

Night purge is what you want. If the windows had been open all night, the house would probably be cool by now.

[Ferdinand]

2 hours ago, SteamyTea said:

What is the house made from?

 

 

Brick and block.

 

Inside the cavity insulation is block.

 

Inside the house is some studwork, some block.

 

F

[SteamyTea]

1 hour ago, Ferdinand said:

Brick and block.

So no better than a timber frame place for limiting temperature then.

[Ferdinand]

1 hour ago, SteamyTea said:

So no better than a timber frame place for limiting temperature then.

 

Wall u value is probably 0.25. Rockwool in the cavity, thermalite inner.

 

F

[SteamyTea]

@Ferdinand

Just collecting evidence for when I get around to writing up my bit about the effects of mass on temperature.