Insulating the roof

[Viking]

We plan to move to my wifes house next year, but we need to fix the roof first. The way it is now is simply too hot for us. The roof is metal and the ceiling is plywood. What method would make the biggest difference compared to the cost? Radiant barrier, insulate the ceiling, solar powered attic ventilation, paint the roof  white or in similar bright color?

Radiant barrier and paint the roof seems like a no brainer to me since it´s not very expensive but what do you think about insulating the ceiling with Rockwool or styrofoam? Any of you have experince of the solar powered attic vents?

Any other sugestions would be appreciated.

[scott h]

48 minutes ago, Viking said:

Any of you have experince

Frankly I think you are fighting a loosing battle, the average temp and humidity is just to high to effectively insulate a house with out spending a lot of money.

When we built our two story house we tried to insure that we had enough ventilation for good air flow and we chose 3 rooms to install split air condition units. 2 bed rooms and a "family" room. During the really oppressive months we spend most of our time in the family room.

This is not a new problem, look at some of the old colonial houses,,,,,,,,,,,,,high ceilings   and huge windows.

[Old55]

We had a thermostatically controlled hard wired attic fan installed in our home here in the States several years ago made a significant reduction in temperature.

[GeoffH]

Just now, Old55 said:

We had a thermostatically controlled hard wired attic fan installed in our home here in the States several years ago made a significant reduction in temperature.

Our house (which we bought not built) has a large fan in the roof of the second floor main bedroom which is in the floor of the third floor common area.  When it is turned on it makes both floor cooler,  it would be even better if it was thermostat controlled!

[sonjack2847]

I have plenty of soffit vents and a mechanical vent and that works great. You could also add the white foil backed insulation and that will also make a difference, along with the light coloured paint on the roof sheets.

[scott h]

This is just me, it is not so much the heat its the humidity that just kill me,,,,,,,,,,,,,,,,,,unless you have a dehumidifier or air kon all you can do is suffer 

[Tommy T.]

Sorry.... I lost the exact information in a computer crash. But a few months ago I Googled "insulation" for my about-to-be-constructed new home and found a company in Manila that supplies all manner of insulation - fiberglass, rock wool, styrofoam. You might try doing  that and see what you can learn?

My personal opinion, for what it's worth, is to paint the roof - as you already thought - in reflective white, install the vents and fans that some here have suggested and also insulate heavily. But that might be too expensive or difficult for your situation - I don't know anything about that. What I suspect is that, with electricity being so expensive here, you should recoup your costs within a few years.

Good luck!

[Dave Hounddriver]

18 minutes ago, Tommy T. said:

My personal opinion, for what it's worth, is to paint the roof

I had a friend, now deceased, who had a nice cool house by putting solar panels all over the roof that the sun hit the most.  Then he hooked into the Noreco main line so all that solar power was fed into the system.  So the electric bill was close to zero.  The solar panels soaked up the sun's rays. And he ran air conditioning for free.

[Tommy T.]

That sounds like an excellent idea. My only questions would be - at what cost and how long to recoup that? I will soon have my own house constructed here, so I am very interested...

[robert k]

If I were building I would look at geothermal. If I lived near running water or a fairly deep pond, I would definitely be putting in some kind of heat exchanger system. Putting a roof over the roof with airflow between the two to keep the sun off would help, the shading roof doesn't have to be water tight, I saw an interesting design at a commercial egg producing facility. Depending on how high the roof is it could be extended so the roof shades the walls through more of the day, problem being that it can't go so low that people walking around the house on the outside walk into the overhang. Think something like a carport all around the house if the roof isn't very high.

In the hot, more dry months, a mister on the roof may help, a mister may make an outdoor split aircon more efficient.

Ive seen construction with foam insulation between 2 block walls. We even used to use some 90mm thick foam in roof construction on top of a concrete roof that would be covered in rubber then tar and gravel, only the top layer of gravel gets hot, but you have a heavy roof about a foot/300mm thick. I would say whatever is cheap and effective is what I would go with, Tyvex to reflect heat on the inner roof side, fiberglass in the ceiling, possibly a misting system on the roof, shade trees. Build a defense in depth from the heat enemy. Aircon will still be necessary to remove humidity and adding direct cooling, but if you plan it correctly, not so much.

I don't know exactly what you are working with but I do suggest that it's never a bad time to get creative to beat the heat except when you want a sauna or hot shower or soak. If the house is owned, I'd be willing to spend more.