Can we discuss effective methods for reducing heat gain ?

[IbeDavid]

Im about to experience ownership of my first Mobile Home in Florida. The 1985 MH i bought faces south with no shade unfortunately. Im looking for proven methods to reduce the heat gain thru the roof and windows . Specific questions i have are : 1. Is Silver Reflective Paint on shingles effective ? 2. Is adding a new ceiling inside and filling the cavity with insulation a viable option , and, is it a common practice ? 3. Ive heard of people putting water sprayers on the roof during extreme hot and prolonged sunny weather to cool the roof thru evaporation and am wondering how effective this is ? Any thoughts on these issues to make the a/c run less/cool better , would be appreciated from someone who is new to MH's and also to living in Florida. Regards.

[Harry]

Hi

I have red shingles. I cooled the attic space more by adding 4 roof vents, perforated soffit and eaves. Also my attic space was a moisture maker so the additional venting helped that cause.

Harry

[Yanita]

Hi,

Not sure about painting shingles, hopefully JD will respond to that.

As for your windows you could use a window tint, or some have bought screens that are tinted, perhaps awnings.

Are you utilizing a ceiling fan.

Since you have an older home I must ask if any upgrades have been done, new windows, doors etc...?

You do not mention the year of your current ac unit, this might need an upgrade as well.

Yanita

[JD]

I don't know about spraying water on roofs for cooling. Not that it would not work, I just don't know about it. Water usage is pretty important in the Central Valley. We get very little rain and are one of the top ag areas of the world.

I also think it is not a good idea to paint shingles with anything. I have never found that the reflecting benefits are worth the expense and possible damage to the roof shingles. The paint dries and then cracks, leaving areas for water to penetrate but not get back out.

Insulating the ceiling could be a good thing. I have found that factory insulation, especially when old, is not as good as it could be. Replacing the insulation with new, full thickness of insulation can sometimes double the R value, depending on what you start with. Still, the insulation should be of consistent thickness across the entire roof, meaning to not pile it up high at the peaks and leave it short at the eaves. This only directs the movement of air to the eaves. Typically, R-19 is the most you can fit into onlder mobile homes and even then it is squishing down at the eaves.

On the roof shingles and insulation, they are both cost effective when those repairs are already required. When you need new roof shingles, go with white shingles. Better yet, go with a different insulated roof system. On the insulation, it is an excellent opportunity to replace insulation when you need to do a large amount of ceiling panel/sheetrock repair. Otherwise, to replace a good ceiling just to replace the insulation would probably not bring you a return on your investment for many years.

Roof venting as Harry noted is the most cost effective way of reducing roof heat into the home.

JD

[IbeDavid]

Thanks for your replies. It was my understanding that a MH doesnt have an attic (?). Is there an air space ? The year of my MH is a 1985 . Thanks.

[JD]

All mobile homes have an air space where an attic would be, so I think it would be considered an attic. Not sure of the technical definitions though. But, this would not be a space a person would crawl around in because of the limited space and strength of construction.

Even a curved top single wide home has this space. At minimum, there will be about 2 1/2" above the eave wall for the end of the truss as it meets the top plate of the wall. Then the curve will usually add about 9" minimum, so this is the height of the space at the middle. Usually, I will see R11 packed across this ceiling, but I have seen thin 1 1/2" fiberglass in this area too, about R7. This insulation could be replaced with the dense fiberglass available now. R-13 for 3 1/2" space, same space as R11.

On a older mobile home with a tip-out type room, the ceiling is usually 2x4's with ceiling panels stapled to the bottom and sheathing or just rolled metal roofing on the top. 3 1/2" space.

JD

[Dean2]

As to roof spaces I think proper insulation,venting and a truly reflective top coating(bright white)are the best bets..

I always wonder about the silver coatings tho,I have had silver cars that absorb heat like any other dark color does,almost like black! Now,if by "silver",they really meant to say "chrome" then I would have to agree,,much more reflective and hence,cooler too.

Many roof coatings actually absorb sunlight,I think,on purpose,to soften it and possibly seal/re-seal any cracking and/or the tar strips found between laid shingles,and,would suspect that Silver Seal type stuff does the same and *possibly* the "reflective" claim is and advertising ploy to make the product more appealing..Maybe somebody should test it out,,feel it in the sun,,then,,feel a dark shingle,,then feel a chrome surface! Every chrome or white surface I remember touching has been cool even in the hottest sun.

Now,if there is an airport nearby,One might wonder if there would be a problem with a super-reflective surface blinding Pilots?! LOL,,or even car Drivers if the surface was lower than the road for example..LOL,might be waaayyyy over-thinking that one tho! Then again?????

Dean

[Yanita]

Hi,

As JD said coating over shingles is not advisable.

This past summer we added an exhaust fan to our vents. Also you might want to consider a turbine roof vent if you live in a breezy area.

Chrome not hot...hmmm, sure is on our Harley in triple degree heat.

Yanita

[IbeDavid]

All mobile homes have an air space where an attic would be, so I think it would be considered an attic. Not sure of the technical definitions though. But, this would not be a space a person would crawl around in because of the limited space and strength of construction.

Even a curved top single wide home has this space. At minimum, there will be about 2 1/2" above the eave wall for the end of the truss as it meets the top plate of the wall. Then the curve will usually add about 9" minimum, so this is the height of the space at the middle. Usually, I will see R11 packed across this ceiling, but I have seen thin 1 1/2" fiberglass in this area too, about R7. This insulation could be replaced with the dense fiberglass available now. R-13 for 3 1/2" space, same space as R11.

If theres a good amount of air space between the ceiling and roof exterior, then is a powered / roof mounted attic fan feasible to put in providing theres enough intake air grilles on the soffit ? Im sure exhausting using an attic fan would REALLY reduce heat buildup in there. Have you seen anybody doing this with a MH ? Thanks.

On a older mobile home with a tip-out type room, the ceiling is usually 2x4's with ceiling panels stapled to the bottom and sheathing or just rolled metal roofing on the top. 3 1/2" space.

JD

[IbeDavid]

Opps..it seems my reply above to JD got a bit misplaced in the text body, so, here is my reply again :

'If theres a good amount of air space between the ceiling and roof exterior, then is a powered / roof mounted attic fan feasible to put in providing theres enough intake air grilles on the soffit ? Im sure exhausting using an attic fan would REALLY reduce heat buildup in there. Have you seen anybody doing this with a MH ? Thanks. '

[JD]

I would think powered gable vents fans would help a lot. That is a lot more movement of air than the home was originally designed to do passively. Harry or one of the other members from high humidity areas might have some personal experience with this. People in your (and every) area have been trying to obtain the best venting system for their climate for a long time. I am sure the effective ways and the mistakes have already been found. It is just trying to get that local info that is important.

My climate is so different than yours, there could be factors that I have never dealt with. I have only been a mobile home repair guy in Fresno, CA. Other than that, I worked a lot of roofing and sheetrock in Arizona, which is much like here but worse and I worked in the NorthWest. We had plenty of cold and wet there, but I was pole barn builder, building garages, horse barns, shops and one building was the biggest private aviary I have ever seen. 30x48 with 12' eaves.

So hopefully we can get some warm humid folks to chime in here. Or better yet, members from warm humid climates!

JD

[JD]

Here in Fresno, CA, I get up on a lot of roofs in 100+ degree heat. White roofs are relatively cool to the touch and aluminum asphaltic coating are hot. Sometimes too hot to touch for long. The white elastomeric is hot also, but it does not feel like it will leave blisters if you don't get your hands off of it.

In California, we now have a Cool Roof rating by the Cool Roof Rating Council. This is a mandatory thing for commercial buildings. There are aluminum coatings that are included in this Cool Roof certified program. I believe they have to be tested at above .70 initial reflectiveness to qualify. Some aluminum coatings are up in the mid 80s. White will still rate higher. All roofs get dirty after a while and lose a lot of this reflectiveness. The program is meant to get commercial buildings away from black and gravel BUR roofing. But these coatings are what people are using on their mobile homes.

JD

[Dean2]

chrome on the Harley is hot? Are We talkin the handlebars,,or,,the exhaust!? I gotta admit,I'm suprised.

Dean

[WildIrish]

One thing that helped us with our west-facing wall was one of those lightweight, reflective emergency blankets. I just taped it to the window frame, and the wrinkles eventually unfolded themselves. Really reduces the incoming heat!