Painting my house non white

geordief

I have an old house with no damp course and very thick stone walls.

Over the years damp has been a problem on the external (and even internal) walls - inside I mean.

Would changing the colour of the exterior paint (from its present white to something darker) be likely to be a great help?
Would that bring heat to the outside wall (esp the South facing one) ?

The idea came to me (perhaps it is common knowledge but not to me) because isn't white the colour used in hot countries -which we don't have - to provide a coolness and wouldn't the opposite provide some warmth to us other folk?

pawrick

white reflects the light, dark absorbs more of it. Type of material affects this also.

Doubt it's going to make a difference in our country as we don't get too much light to begin with and it's not that warm anyhow but someone else I'm sure knows more.

Gurgle

geordief wrote: »

Would changing the colour of the exterior paint (from its present white to something darker) be likely to be a great help?
Would that bring heat to the outside wall (esp the South facing one) ?

Yes, good idea. Black or very dark blue would be best.

geordief

pawrick wrote: »

white reflects the light, dark absorbs more of it. Type of material affects this also.

Doubt it's going to make a difference in our country as we don't get too much light to begin with and it's not that warm anyhow but someone else I'm sure knows more.

whenever you heary talking about solar energy (or just going out in the sun generally) they point out that even daylight (as opposed to direct sunshine) is quite powerful.

BryanF

paint will make very little difference

geordief wrote: »

Would changing the colour of the exterior paint (from its present white to something darker) be likely to be a great help?

no

Would that bring heat to the outside wall (esp the South facing one) ?

no

The idea came to me (perhaps it is common knowledge but not to me) because isn't white the colour used in hot countries -which we don't have - to provide a coolness and wouldn't the opposite provide some warmth to us other folk?

no

what is it you want to solve?

I have an old house with no damp course and very thick stone walls.
Over the years damp has been a problem on the external (and even internal) walls

so solve the dampness issue by finding the source of moisture. it will most likely be either water egress, rising damp or lack of ventilation combined with lack of insulation.

geordief

BryanF wrote: »

paint will make very little difference

nonono

what is it you want to solve?

so solve the dampness issue by finding the source of moisture. it will most likely be either water egress, rising damp or lack of ventilation combined with lack of insulation.

You don't say why paint will make no difference.
I appreciate the first port of call is to solve the source of moisture but when you do not have a damp course then that is an expensive issue to solve.

If the temperature of the outside wall can be raised by a few degrees (on average) over the course of the winter and that temperature rise is transmitted across the width of the wall into the interior then wouldn't that have the effect of reducing dampness in the interior side of the (external ) wall?

I realise that the sun is not going to appreciably raise the temperature of an inside wall on a daily or hourly basis but I wonder if a small continuous rise in temperature in the wall over the winter as a whole would have a beneficial (even if not completely remedial) effect on levels of moisture in the wall?

sydthebeat

The rate of heat loss by radiation compared to convection is negligible. All you would be doing is augmenting the radiation heat loss while not affecting the vastly more significant convection heat loss.
yes the surface of the wall will become slightly hotter if it was black than white, but in turn you would be increasing the temp differences between the two surfaces of the wall and thus increasing the convection heat loss.
Also, conversely, a black surface looses heat quicker than a white surface so when the irradiation isn't forthcoming ie night-time, then the heat loss through the black surface is higher from a radiation heat loss point of view.

geordief

thanks for all the replies.It seems like a complicated equation.

Actually the rooms in question aren't heated very much in winter (they do get plenty of sunshine though) so I don't think convection is such an issue.

But if the black surface does indeed cool down appreciably quicker at night than a white surface then that would be a game changer and negate the hypothetical benefits of a darker suface when the sun is shining.

BryanF

geordief wrote: »

You don't say why paint will make no difference.

thanks Sydthebeat for answering this.

I appreciate the first port of call is to solve the source of moisture but when you do not have a damp course then that is an expensive issue to solve.

is it? I would ask you consider and define what you consider expensive Versus you a your family's potential health problem by ignoring this dampness..

If the temperature of the outside wall can be raised by a few degrees (on average) over the course of the winter

what! by paint?!

and that temperature rise is transmitted across the width of the wall into the interior then wouldn't that have the effect of reducing dampness in the interior side of the (external ) wall?

no, i dont believe so.

I realise that the sun is not going to appreciably raise the temperature of an inside wall on a daily or hourly basis but I wonder if a small continuous rise in temperature in the wall over the winter as a whole would have a beneficial

no

(even if not completely remedial) effect on levels of moisture in the wall?

no

lets back-up a second here. you want to paint your house black and you expect this to in some way reduce your dampness problems? as someone who has worked and specified solution on many old buildings, this makes no sense to me. there is a good chance that the type of paint & maybe plaster is actually adding to your moisture problems. was this old house built of stone, lime, maybe even mud? was it originally lime-washed? has the external ground level changed/risen since it was built? have you changed the windows, added insulation, changed how heat has been delivered? all these things are likely to have had more of an impact on your dampness/condensation issues and way more relevant than painting your home black..

if you check back through the boards.ie threads , you will find several where damp/condensation and breathable wall issues are discussed and insulation, ventilation and remedial damp course solutions are offered

sydthebeat

geordief wrote: »

thanks for all the replies.It seems like a complicated equation.

Actually the rooms in question aren't heated very much in winter (they do get plenty of sunshine though) so I don't think convection is such an issue.

But if the black surface does indeed cool down appreciably quicker at night than a white surface then that would be a game changer and negate the hypothetical benefits of a darker suface when the sun is shining.

Convection is the only significant issue.

Convection is heat loss through the material in the wall. This is where you are loosing most of your heat.
As bryanf says above, if the point of this exercise is to stop the damp, then you must identify the reason for the damp in the first place. You seem to be coming at it from the view point that condensation due to heat loss is causing the damp.

BryanF

geordief,
here you suggest your going to lock in the walls dampness??
http://www.boards.ie/vbulletin/showthread.php?p=77642960 -I would strongly recommend you invite a lime plasterer round and listen to what they have to say (I can recommend a few if you wish) and then use a breathable paint finish

and here you show that the internal to external level difference of your walls is not adequate and probably adding to the rising damp issues
http://www.boards.ie/vbulletin/showpost.php?p=77965597&postcount=4
may i suggest you look at how you could external add a French drain around the house, to elevate the rising damp issue.