Thread: Roof Ventilation thoughts ?

OK,
So I finally have someone from PD House who is earnestly communicating with me and actually trying to answer my questions ASAP. It's like a breath of fresh air and makes me feel a little better about our project in Nakhom Pathom.

But, I'm confused about one thing. On the front of our house, we will have a louver grate looking thing above the main entrance. It should look similar to the model design of our house.




I had always assumed it was a functioning device, but I was told it is decorative only. So I then asked how will hot, humid air vent out from under the roof, especially since we have vented soffits all the way around. I was telling her that I will have to look at ventilators.

This was her response:

The roof tiles used in your home is known as Roman tile. When install, each row of the tiles overlaps the row of tiles below by 8-10 cm. and there is a gap between 1-3 mm. in height where the tiles overlap. These gaps allow natural airflow and circulation.

To allow cool air entering the roof space, vented soffits are installed along the roof line. This will allow the cooler air to get into the roof space and displacing the warmer air through the many gaps between the tiles as described above. The construction described above is a common practice from the roof tiles manufacturer in Thailand, SCG.
...


You mentioned that you will add the ventilators on the roof. We suggest you to live in the house for a while to compare the temperature inside the living areas and outside the house before you make decision on the ventilators. After comparing the temperature inside and outside, if you would like to install the ventilators, the risk that you may have to consider is water leaking since the roof will be modified. Our houses won 17 Energy Saving House Awards, in Year 2011, from Department of Alternative Energy Development and Efficiency, Ministry of Energy. Two of them are model WA-947 (same as your house) and None of those 17 houses required additional ventilator on the roof.

Any thoughts/comments from the more experienced folks ? I never noticed any gaps in the roof tiles, although I wasn't looking for that kind of detail either. I'm used to shingle style roofing in the USA, so I'm not familiar with the nuances of these tile roofs.

Thanks,
Steve

get up into the roof space and see if you can see daylight with those roof tiles, that will vent the roof.
cpac monier tiles are able to do this, not sure about yours.
EDIT:just looked at your tiles in your other thread, and they are pretty much the same as cpac monier so I would say yes they are self ventilating.

Probably true; in Thailand they don't have the second layer of roofing felt so there are small gaps between the tiles

mind you, that also allows rain to get blown in when there are storms...

One of the reasons a gable end roof is better than a cottage roof?

Get a couple of these mounted on your roof - they work:

Originally Posted by stevefarang

When install, each row of the tiles overlaps the row of tiles below by 8-10 cm. and there is a gap between 1-3 mm. in height where the tiles overlap.

That means the hot air has to perform an S bend to get vented.
I would install 3 or 4 vents to make sure the hot air vents easily.
Most manufacturers sell these vents to match their tiles.

The CPAC ones look like this

We had tile with wirlybird ventilators and added one of these.
took about 2 deg off the room temp.
Rand Solar Powered Attic Fan 27 Watt w Roof Top Ventilator New | eBay

Originally Posted by Necron99

We had tile with wirlybird ventilators and added one of these.
took about 2 deg off the room temp.
Rand Solar Powered Attic Fan 27 Watt w Roof Top Ventilator New | eBay

They have the rotating whirlygig ventilators at Home Pro, Home Mart, Thai Watsadu, - pretty much all over building supply places here in Thailand.

The roof tiles used in your home is known as Roman tile. When install, each row of the tiles overlaps the row of tiles below by 8-10 cm. and there is a gap between 1-3 mm. in height where the tiles overlap. These gaps allow natural airflow and circulation.

Bullshit, some tiles might have a 1mm gap and that's probably because of wrong installation (even if tiles have a small gap it won't be sufficient ventilation). Please note that it also depends on the kind of tiles, there are a few different Roman tiles and most of them hook into each other at the overlap making sure that there is no gap between them.



Now it's very easy to get your roof ventilated, often it's done as shown in the picture below, just get a ventilated rafter or whatever you call it in English (or one with holes in it). Of course also get precautions at the roof ridge.

Thanks all for the replies and feedback. As I said, I was considering some of those whirlybirds.

Koetjeka, just an FYI. The drawing you supplied doesn't match our wall arrangement. We have soffit vents extending all the way around and the roof extends outwards. Here's a shot, looking out one window:





And a view of the roofing tiles. You can also see the soffit vents:






I'm not sure I want to go and mess around with the roof ridge at this time. I think the whirlybirds would be the better way to go.



Steve

Aren't PD house the biggest cheaters around ?

Originally Posted by stevefarang

Thanks all for the replies and feedback. As I said, I was considering some of those whirlybirds.

Koetjeka, just an FYI. The drawing you supplied doesn't match our wall arrangement. We have soffit vents extending all the way around and the roof extends outwards. Here's a shot, looking out one window:

I know it doesn't match (don't see a lot of cavity walls in Thailand), I just wanted to explain.

I now also know what soffit vents are, I've never seen those before (because in my country we rarely ventilate the roofs). I now also understand your question to PD house better. I think it's quite simple; soffit acts as air inlet but you don't have an outlet (nor any ventilation without this outlet), it's kind of like blowing into a straw but closing the other end I guess.

As a solution you can indeed use an ugly whirlybird or maybe you can find one of these, which are imho far more beautiful. I'm not 100% sure if it can act as an outlet, I think so because of the pressure difference.




Most beautiful solution would of course be to use this kind of stuff as it's invisible.

Koetjeka,
Yes, that space has to be able to "breathe".

I'm not going to and rip up the whole ridge to install anything like that first one, especially if it doesn't match the existing tiles. That second one looks like water would easily get in.

I don't think the whirlybirds will look too bad, if they are low profile and hidden on the south side (back side) of the house. I'll wait a year or so and see how well the existing roofing system will ventilate on it's own.

Thanks for your input !

Steve

Originally Posted by peterpan

Whirly vents rely on external force (wind) to work, have you not noticed that in Thailand there is little wind? for certain they rotate, but that energy is supplied by the thermal head generated by the difference in temp, inside to outside. so if you have a natural draft why to you need whirlys? in other words they don't work here, despite the rotating whirly being rotated by internal pressure.

Are you sure about that? If they move then they'll create a draft.

Originally Posted by peterpan

Whirly vents rely on external force (wind) to work, have you not noticed that in Thailand there is little wind? for certain they rotate, but that energy is supplied by the thermal head generated by the difference in temp, inside to outside. so if you have a natural draft why to you need whirlys? in other words they don't work here, despite the rotating whirly being rotated by internal pressure.

It's not that bad with the wind here in Thailand right? Here in Isaan there is always some wind (my guess at least 1 Bf. all the time). Also I don't think you actually need the wind for them to work as warm air rises and can still leave through the gaps in this whirlybird?

Originally Posted by peterpan

Whirly vents rely on external force (wind) to work, have you not noticed that in Thailand there is little wind? for certain they rotate, but that energy is supplied by the thermal head generated by the difference in temp, inside to outside. so if you have a natural draft why to you need whirlys? in other words they don't work here, despite the rotating whirly being rotated by internal pressure.

Actually, before the walls went up, we always noticed a nice breeze, upstairs, at our house project. Enough that I'm planning on including some little wind generators along with the solar cell project I'll be doing on site, after the house is finished.

If I felt there was enough of an exit point, I wouldn't be worried about natural draft. But if there is a thermal head to drive the whirly, then that higher temperature air, rising up, has to come from somewhere (ie up through the soffit vents and heated in the roof space). So, it works anyway. I just don't want a stagnant mass of humid air under the roof structure. I want that space to be able to "breathe".

Steve