Re: painting roof white to reduce heat inside the house

is your roof GI , Ceramic or Cement?

Re: painting roof white to reduce heat inside the house

roof is GI

Re: painting roof white to reduce heat inside the house

you will have to douse it with acid etching solution (boysen has it but most of the depot stores dont carry this so you may have to call boysen for availability) so the GI layer gets
micro pore/scratches-a-majig 🙂

Then enamel paint would be be best and cost effective. I am not sure what the paint they use on the road though and i am not sure if it for masonry only, which might be latex based.

Be better if it is spray painted in several thin coats. Brushing may cause peeling after awhile.

This is by far not a professional opinion but is just somethingi would do

Re: painting roof white to reduce heat inside the house

It's an old house, and the roof has already been painted previously oxide red, not sure how many times before. do I still need the acid etching solution?

Re: painting roof white to reduce heat inside the house

acid etching will only work on fresh metal surface

Re: painting roof white to reduce heat inside the house

I'm seriously thinking of painting our roof white to reflect at least some of the heat. i'm thinking of using the stuff they used to paint sidewalks with. what is that stuff called and where can I get it?

Coating with white paint will decrease the heat absorption of the G.I. roof by only minimal percentage. if you really want to deflect the heat on your roof, try the cermamicoat of Flexseal. But most small hardwares don't have them, its by order. try to drop by at wilcon depot.

Re: painting roof white to reduce heat inside the house

Boysen has Reflectorized Traffic Paint, white and yellow.
Davies has Traffic Paint, white and yellow, regular and reflectorized.

I don't know whether this is what the government actually uses to paint lane markings, etc. on roads, or whether this is appropriate for metal roofs.

Re: painting roof white to reduce heat inside the house

Coating with white paint will decrease the heat absorption of the G.I. roof by only minimal percentage. if you really want to deflect the heat on your roof, try the cermamicoat of Flexseal. But most small hardwares don't have them, its by order. try to drop by at wilcon depot.

curious to where you got this info from el camarote. what do you mean by minimal? any figures?

Re: painting roof white to reduce heat inside the house

curious to where you got this info from el camarote. what do you mean by minimal? any figures?

Here's the link for your info:
http://www.scientificblogging.com/news_articles/white_roofs_could_reduce_urban_heat_island_effect_33_percent

As to what percentage do Flexseal does to your roof:
http://www.campbridge.com/p_cera.html

Hope these links can satisfy your curiosity. 😮
Figures are given.

Re: painting roof white to reduce heat inside the house

Here's the link for your info:
http://www.scientificblogging.com/news_articles/white_roofs_could_reduce_urban_heat_island_effect_33_percent

As to what percentage do Flexseal does to your roof:
http://www.campbridge.com/p_cera.html

The first link confirms the general idea of what I want to do, though the type of paint is never mentioned. however, the second link looks like misleading advertising to me. its says:

...much like the ceramic coating used to shed 95% of the heat generated upon re-entry of the NASA's space shuttles... Shields heat by at least 6 degrees Celsius.

as a former advertising person i'll be wary of such claims. likewise, why would you say that..:

Coating with white paint will decrease the heat absorption of the G.I. roof by only minimal percentage.

are you are connected with this product?

Re: painting roof white to reduce heat inside the house

Re FlexSeal 'ceramic' paint -- hard to say whether it is misleading or promising. Not enough posted info on the effectiveness of the actual product, as opposed to ceramics in general.

Best to call them up and ask if they have and can provide:
- results and description
- of actual controlled tests
- of the actual product (not NASA shuttle tiles or other brands)
- done in the Philippines (not by testing bodies abroad, e.g., ASTM, of similar materials abroad).

If you look into this, let us know what you find out.

Re: painting roof white to reduce heat inside the house

I would actually agree with El Camarote that having the roof painted white (or reflective) may not have a very significant decrease in Temperature.

Also if you observe Chicken coops and tunnel vented atmosphere controlled piggery houses. They dont have the roofs painted white. These are designed by engineers in pig eating countries like Canada , USA and England. If the reflectivity of the roof can decrease heat significantly then all these structures wouldve been painted white.

conductive heat i suspect is still the major problem. Radiative heat is only a portion of heat product by the sun afterall. Its like if you leave a white t shirt and a black t shirt outside. eventually both temperatures will be almost equal after achieving equilibrium (which doesnt take long especially due to humidity)

Ceramic on the other hand... dunno 😛 all i know ceramic composites are pretty scratch proof. Great for watches 🙂

Re: painting roof white to reduce heat inside the house

I would actually agree with El Camarote that having the roof painted white (or reflective) may not have a very significant decrease in Temperature.

dude, i'm not looking to have 20 degrees inside my house without air conditioning. the primary objective is to get the room temp to be at least 2 to 5 degrees below body temp. and yes it was 38 degrees inside my house yesterday. ambient temp was actually cooler at 36.5

Also if you observe Chicken coops and tunnel vented atmosphere controlled piggery houses. They dont have the roofs painted white. These are designed by engineers in pig eating countries like Canada , USA and England.

IIRC these pig eating countries are not in the tropics. these houses need to retain heat not the other way around

conductive heat i suspect is still the major problem. Radiative heat is only a portion of heat product by the sun afterall. Its like if you leave a white t shirt and a black t shirt outside. eventually both temperatures will be almost equal after achieving equilibrium (which doesnt take long especially due to humidity)

I disagree with this. radiation reflected is not absorbed. less heat absorption means that the heat can dissipate faster. I've built a solar cooker before and I know that color does makes a huge difference in the amount of energy absorbed. a white roof and a black roof will never have the same surface temperature when exposed to solar radiation for the same period of time. are you so sure about the t-shirt thing? will you be willing to stand out in the sun with me in a white shirt and a white hat and you wearing a black shirt and a black hat to see who passes out first? 😀

Re: painting roof white to reduce heat inside the house

These countries design these atmospheric houses for poultry and piggeries from africa to central and south america and philippines. Pigs and chickens thrive best at 20 degrees and some species around 18 degrees (although this is besides the point hehehe 🙂 )

Solar cooker does take the advantage of reflective surfaces. But do observe that the sun's reflection are redirected to a single point by virtue of a parabolic shaped reflector bowl

White tshirt and black t shirt example is used to illustrate final temp when Equilibrium is achieved. Of course, I , in the black shirt will pass out earlier than you, in the white tshirt. But trust me you too will pass out perhaps a couple of hours later only. Hence if a reflective roof can thwart the increase of the inside temp only by a few hours before it achieves equilibrium, then its not really worth it.

Best way to dissipate heat in an enclosed environment is to have air exchange (this is assuming full-on insulation is just too costly to be practical and air conditioning is just ..well bloody expensive) from the outside air (if it is cooler, which in your case, it is)