Jump to content

Roof paint colour - light or dark?


Grassman

Featured Posts

My boat had a dark blue roof for years. When we had a very hot summer a few years back I repainted it pale blue and the difference it's made is huge. I suspect last summer would have been unbearable previously. 

ETA you do get glare from gloss, more on the light colour, but I reckon the trade off is worth it. 

Edited by Arthur Marshall
Link to comment
Share on other sites

Colour change made a MAHOOSIVE difference on my bote.

 

Roof and sides were both midnight blue when I bought the the bote and inside was unbearably hot inside on sunny summer days, to my surprise.  Previous boat had midnight blue sides and raddle grey roof and was fine.  Both boats have rockwool insulation.

 

I had the roof painted pale blue and what a change! Interior is now fine in sunny weather. 

Link to comment
Share on other sites

I’d go for a red oxide/ raddle red cabin top every time. Serviceable, easy to touch up or recoat, pretty non slip without sand or other additives, and without reflective and dazzle issues. We never had issues with heat in summer, probably due to Spayfoam insulation beneath. I am, of course, a staunch traditionalist.....

Link to comment
Share on other sites

1 hour ago, Athy said:

...and a surprising one from a man who has himself changed his forum name in the past.

I would respond in some detail to that Mike but tbh I cannot be bothered.

Link to comment
Share on other sites

Well - the Bedouins wear black clothing in the desert and it keeps them cool.

Scientific tests prove there is no difference in 'body temperature' between wearing white and black clothing

 

Each of the test sessions (black-robed, white-robed, uniformed and half-naked) lasted 30 minutes. They took place in the Negev desert at the bottom of the rift valley between the Dead Sea and the Gulf of Eilat. The volunteer stood in temperatures that ranged from a just-semi-sultry 35C (95F) to a character-building 46C (115F). Though he is now nameless, this was his day in the sun.

The results were clear. As the report puts it: "The amount of heat gained by a Bedouin exposed to the hot desert is the same whether he wears a black or a white robe. The additional heat absorbed by the black robe was lost before it reached the skin."

 

https://www.nature.com/articles/283373a0

Link to comment
Share on other sites

5 hours ago, Greyladyx said:

I've been around the block MJG? Seen it heard it felt it and lived their.

 

Dont take me for a MUG.

 

Stop the mind games that's why nothing changes.

 

 

This is partly why I made the comment, "could be that you haven't changed"  You chose to see that comment as negative even perhaps as from a "bully"  Your online 'friends' pile in with their support against the perceived threat.  I  added the comment later that we dont really change, we adapt.  But assuming my words are meant to hurt just from a brief glimpse of my posts on other topics and that others play mind games might also mean you struggle to accept any comments that dont make you feel warm and happy....  "the past portrays"  Indeed it does, but not everybody uses childish language to 'speak' online nor adds emoticons to excuse or gentrify a remark. If written comments can be taken many ways then the reader takes them where they like, and usually prefer. 

Link to comment
Share on other sites

This is an interesting discussion (well, mostly!) because I rather thought the idea that black absorbs heat and white reflects it was universally accepted. Clearly not. 

 

My roof is off white raddle and I currently have a black slide.  You could fry an egg on the slide at times when the roof feels relatively cool. Maybe the insulation neutralises the effect it has on the inside of the boat, but black metalwork is definitely hotter than white in the sun.  The slide WILL change colour this year! :D

 

Link to comment
Share on other sites

31 minutes ago, rgreg said:

Or the opposite: good insulation  will prevent the heat being transferred to the boat interior.

I've serious insulation between the metal roof and the wood panelling, can't remember the name of the stuff but it's supposed to be the equivalent of about six inches of loft insulation, and I used double thickness in the roof and sides of the boat.  That does make quite a difference in extreme weather, I think, but I did still notice a considerable improvement in hot weather when i repainted the roof.

Link to comment
Share on other sites

48 minutes ago, Winn said:

This is partly why I made the comment, "could be that you haven't changed"  You chose to see that comment as negative even perhaps as from a "bully"  Your online 'friends' pile in with their support against the perceived threat.  I  added the comment later that we dont really change, we adapt.  But assuming my words are meant to hurt just from a brief glimpse of my posts on other topics and that others play mind games might also mean you struggle to accept any comments that dont make you feel warm and happy....  "the past portrays"  Indeed it does, but not everybody uses childish language to 'speak' online nor adds emoticons to excuse or gentrify a remark. If written comments can be taken many ways then the reader takes them where they like, and usually prefer. 

Sorted now.

Link to comment
Share on other sites

2 hours ago, The Welsh Cruiser said:

I wonder why I noticed no difference when I changed to a lighter colour? Maybe it's down to bad insulation.

There may have been a difference, but it was obviously imperceptible to you and that's an important consideration. As for your insulation, that's a variable that wasn't changed when you painted the roof a lighter colour, so experimentally it's valid. In fact the better the insulation the less effect one would expect paint colour on the outside to have, so your experience seems to show that colour is not a significant factor in heat absorption on your boat.

Link to comment
Share on other sites

3 hours ago, dave moore said:

I’d go for a red oxide/ raddle red cabin top every time. Serviceable, easy to touch up or recoat, pretty non slip without sand or other additives, and without reflective and dazzle issues. We never had issues with heat in summer, probably due to Spayfoam insulation beneath. I am, of course, a staunch traditionalist.....

Ours was red but when the boat was painted we were persuaded to go for grey. From a practical point of view I cant see a difference but I prefer the look of it. Like Dave, no none slip additive but never had a problem and I use the roof in most locks. The paint is Epiphany's if I have spilt it write 

Link to comment
Share on other sites

What were we talking about? Oh, I remember, light / dark roofs. I have painted our roof with light grey deck paint (without grit)  the finish is not beautifully smooth nor is it glossy but its safe to walk on and doesn't show the dirt too badly and being deck paint is quite hardwearing. I think I got it from T.A.Industrial paints Wolverhampton. Boat is in France so roof and decks can get too hot to walk on without shoes and also v. hot for the dog.

Also quick edit just to say that it can be hard to find deck paint without grit. These people sell it, obviously I have no connection.

Edited by Bee
Link to comment
Share on other sites

Insulation on a steel boat will generally work better in winter than it does in summer. The schematic below is based on sprayfoam insulation bonded to steel but I think the same would apply to expanded polystyrene boards or rockwool.

 

In summer solar radiation heats up the steel and the hot steel heats up the insulation. It doesn't matter how good or how thick the insulation is, eventually on a hot summer day in direct sunshine a significant amount of thermal energy will get through. In winter, warm air comes into contact with the insulation and some of the thermal energy will get through the insulation, but not to the same extent as it does going the other way in summer.

 

 

 

 

Presentation1.jpg

Link to comment
Share on other sites

3 hours ago, Arthur Marshall said:

My boat had a dark blue roof for years. When we had a very hot summer a few years back I repainted it pale blue and the difference it's made is huge. I suspect last summer would have been unbearable previously. 

ETA you do get glare from gloss, more on the light colour, but I reckon the trade off is worth it. 

You wrote my reply for me :D

 

Years of a dark blue roof (Midnight Blue) followed by the last 3 years light blue. I was surprised at the difference. The trade off is that light blue  shows the dirt more..

 

Frank

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.