John Jeffkins Posted June 20, 2018 Share Posted June 20, 2018 Evening. I am having a problem with a new engineered timber front door which has a man made core and oak veneer surface. The door is painted in three coats with quality paint and has a dark grey finish. The door faces east and is well protected from the rain. Over the past few weeks on sunny afternoons, the door warps approximately 6mm and then returns to its straight shape sometime the next day. The door supplier says this is because the paint system isn't stopping the UV radiation and are refusing to do anything. Surely no paint can stop the warming effect of the sun and as the paint is dark grey presumably it is actually increasing the heating effect. Can anyone talk me through the science so I can go back to the door manufacturer and argue my case. Any advice would be appreciated as the door was quite expensive. regards John Link to comment Share on other sites More sharing options...
StringJunky Posted June 20, 2018 Share Posted June 20, 2018 27 minutes ago, John Jeffkins said: Evening. I am having a problem with a new engineered timber front door which has a man made core and oak veneer surface. The door is painted in three coats with quality paint and has a dark grey finish. The door faces east and is well protected from the rain. Over the past few weeks on sunny afternoons, the door warps approximately 6mm and then returns to its straight shape sometime the next day. The door supplier says this is because the paint system isn't stopping the UV radiation and are refusing to do anything. Surely no paint can stop the warming effect of the sun and as the paint is dark grey presumably it is actually increasing the heating effect. Can anyone talk me through the science so I can go back to the door manufacturer and argue my case. Any advice would be appreciated as the door was quite expensive. regards John It might be the veneer not allowing the door to expand uniformly when it warms up i.e. different coefficients of expansion between the timbers. Link to comment Share on other sites More sharing options...
swansont Posted June 20, 2018 Share Posted June 20, 2018 I doubt it's UV. It could be a plain old thermal issue — the door heats up and expands, the core expands a different amount, or the interior part of the door expands a different amount (it's cooler) and it warps as a result. UV exposure is not the primary cause of the heating. The bulk of that is from visible and infrared light. I'm not sure how to calculate the amount of warp from differential expansion, though. 1 Link to comment Share on other sites More sharing options...
John Jeffkins Posted June 20, 2018 Author Share Posted June 20, 2018 4 minutes ago, StringJunky said: It might be the veneer not allowing the door to expand uniformly when it warms up i.e. different coefficients of expansion between the timbers. I'm sure you are both right, the door is veneered inside and out and obviously the outside is getting much warmer. The problem is that the door manufacturer is blaming the paint manufacturer saying "it is the paint system that offers the UV protection for the door and it is the UV which is causing the thermal bow" This is clearly nonsense to me but the only way I can debunk there argument is with Scientific response, hence my plea for advice. Link to comment Share on other sites More sharing options...
StringJunky Posted June 20, 2018 Share Posted June 20, 2018 2 minutes ago, John Jeffkins said: I'm sure you are both right, the door is veneered inside and out and obviously the outside is getting much warmer. The problem is that the door manufacturer is blaming the paint manufacturer saying "it is the paint system that offers the UV protection for the door and it is the UV which is causing the thermal bow" This is clearly nonsense to me but the only way I can debunk there argument is with Scientific response, hence my plea for advice. Swansont is a physicist and this will be elementary knowledge for him. Infra-red and plain old convection on one side of the door will be more prevalent than UV,. UV is more energetic than IR but it is not heat per se.... it's not what warms things up. Your door supplier is talking rubbish. Link to comment Share on other sites More sharing options...
Sensei Posted June 20, 2018 Share Posted June 20, 2018 (edited) 43 minutes ago, swansont said: I doubt it's UV. It could be a plain old thermal issue I agree. There is too few UV photons alone to cause such effect. 1 hour ago, John Jeffkins said: Surely no paint can stop the warming effect of the sun Surely color of paint can decrease warming effect of the Sun, if you will use whitish (reflective) colour... 1 hour ago, John Jeffkins said: Can anyone talk me through the science so I can go back to the door manufacturer and argue my case. It will be probably pointless. Because what do you expect? Replacement? Replacement to the same color door the most likely will end up the same effect as you have already.. Replacement to different color door? White? (It probably won't match other elements of house) Return of money? And then what you will have instead of door? There are paints which can change characteristics of how much surface is reflective or transmissive. https://en.wikipedia.org/wiki/Optical_coating If you could get access to IR camera, you could measure temperature of your door.. then paint a bit of it with some reflective (transparent) paint, and compare the next day whether that area has smaller temperature (on IR camera screen!).. Edited June 20, 2018 by Sensei Link to comment Share on other sites More sharing options...
John Jeffkins Posted June 20, 2018 Author Share Posted June 20, 2018 1 minute ago, StringJunky said: It might be the veneer not allowing the door to expand uniformly when it warms up i.e. different coefficients of expansion between the timbers. Im sure you are right, the door is veneered inside and out and obviously the outside is getting much warmer. The problem is that the door manufacturer is blaming the paint manufacturer saying 11 minutes ago, Sensei said: I agree. There is too few UV photons alone to cause such effect. Surely color of paint can decrease warming effect of the Sun, if you will use whitish colour... It will be probably pointless. Because what do you expect? Replacement? Replacement to the same color door the most likely will end up the same effect as you have already.. Replacement to different color door? White? (It probably won't match other elements of house) Return of money? And then what you will have instead of door? There are paints which can change characteristics of how much surface is reflective or transmissive. https://en.wikipedia.org/wiki/Optical_coating Wow, thats a negative response. Are you saying there are no engineered timber doors out there that can be painted grey and not warp in June sunshine. Link to comment Share on other sites More sharing options...
StringJunky Posted June 20, 2018 Share Posted June 20, 2018 (edited) 21 minutes ago, Sensei said: I agree. There is too few UV photons alone to cause such effect. Surely color of paint can decrease warming effect of the Sun, if you will use whitish (reflective) colour... It will be probably pointless. Because what do you expect? Replacement? Replacement to the same color door the most likely will end up the same effect as you have already.. Replacement to different color door? White? (It probably won't match other elements of house) Return of money? And then what you will have instead of door? There are paints which can change characteristics of how much surface is reflective or transmissive. https://en.wikipedia.org/wiki/Optical_coating If you could get access to IR camera, you could measure temperature of your door.. then paint a bit of it with some reflective (transparent) paint, and compare the next day whether that area has smaller temperature (on IR camera screen!).. I have never heard of a door's designed stability being dependent on the colour of paint used. You are way off the mark. It's ridiculous. The door is plainly poorly engineered for that environment. It's possibly a door designed for internal use and it''s been wrongly specced for external use. Edited June 20, 2018 by StringJunky Link to comment Share on other sites More sharing options...
Sensei Posted June 20, 2018 Share Posted June 20, 2018 11 minutes ago, John Jeffkins said: Wow, thats a negative response. I am surprised by your comment. I was simply honest.. Don't you like honest people? what are your expectations from manufacturer of the door.. ? Questions what do you want from manufacturer are insulting you? How come? It appears so you want something (some action) from manufacturer, and they have no idea what do you want from them, and they have no idea how to fix it (probably never had such customer, search the net if somebody else complained prior you!).. (or they have exact idea that their door is crap product, and simply lying to you... but still there are questions: what do you want from them? what action? return of money? replacement?) Sorry, honestly, but nobody will do this investigation for you.. Link to comment Share on other sites More sharing options...
John Jeffkins Posted June 20, 2018 Author Share Posted June 20, 2018 Sensei I dont want an investigation. I asked for help debunking my door suppliers argument that UV was the cause. Others, more helpful than yourself, have pointed out that its Infrared radiation causing the door to heat up. As for what I want, well a refund, so I can buy a better constructed door. Link to comment Share on other sites More sharing options...
Sensei Posted June 20, 2018 Share Posted June 20, 2018 (edited) 49 minutes ago, StringJunky said: I have never heard of a door's designed stability being dependent on the colour of paint used. You are way off the mark. It's ridiculous. We have too little data to make any judgment. That's why I asked to use IR camera to check temperatures inside house and outside, in the worst cases.. 49 minutes ago, StringJunky said: The door is plainly poorly engineered for that environment. It's plausible. John Jeffkins didn't say which country, which state, he is living.. Something which works good in Canada, or Europe, not necessarily will work in Florida or Texas, or Mexico etc. etc. But how manufacturer will learn about it.. ? The most likely only from customers experiences.. 15 minutes ago, John Jeffkins said: I asked for help debunking my door suppliers argument that UV was the cause. Others, more helpful than yourself, have pointed out that its Infrared radiation causing the door to heat up. That's what I said in the first row of my the first reply "I agree. There is too few UV photons alone to cause such effect.".... 15 minutes ago, John Jeffkins said: I dont want an investigation. That's wrong. Because you would truly understand the nature of the problem. And be able to prevent in the future.. or even warn other customers to not make the same "mistake"... 13 minutes ago, John Jeffkins said: that its Infrared radiation causing the door to heat up. As for what I want, well a refund, so I can buy a better constructed door. You might not need any refund.. any new door.. simply you might just need transparent paint, which will reflect more photons, which will prevent from heating it up.. Edited June 20, 2018 by Sensei Link to comment Share on other sites More sharing options...
swansont Posted June 20, 2018 Share Posted June 20, 2018 6 minutes ago, John Jeffkins said: that its Infrared radiation causing the door to heat up. As for what I want, well a refund, so I can buy a better constructed door. And visible, which is only slightly less power than the IR. All light from the sun will cause it to heat up. Quote Of the light that reaches Earth’s surface, infrared radiation makes up 49.4% of while visible light provides 42.3% 9. Ultraviolet radiation makes up just over 8% of the total solar radiation. https://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/ Link to comment Share on other sites More sharing options...
studiot Posted June 20, 2018 Share Posted June 20, 2018 Hello Jeff, I really sympathise with your predicament as I am living with a very expensive defective front door supposedly engineered to replace the original oak one after 65 years of service. Sensei is both right and wrong. You have mentioned a warping of 6mm which suggests you are in a metric country, ie not North America. But he is right insofar as you have not supplied sufficient information. Firstly what do you mean by 6mm warping? How is the door fixed? Did the frame come as part of the door-set? Who installed it? You say it is well sheltered. Does that mean that part of the door is in shadow and part fully exposed? You say it has a lightweight core with oak veneer, which means it probably has low thermal capacity, especially in the core, but more details are needed. Who decided that a composite door was suitable for this location and why? Why are you painting an oak door, veneered or not? What is the detailed construction of the door? Without these details it is impossible to make a rational assessment of the causes. Assuming the framing is sound and unmoving, I would start by looking for differential heating in the sun's rays, regardless of wavelength and work from there. Link to comment Share on other sites More sharing options...
John Jeffkins Posted June 20, 2018 Author Share Posted June 20, 2018 2 hours ago, StringJunky said: It might be the veneer not allowing the door to expand uniformly when it warms up i.e. different coefficients of expansion between the timbers. STUDIOT thanks for your interest. I am in South East England. The door warps along its length, it bows in, which is counter intuitive. The door was fitted by a professional, with three100mm hinges, fixed securely to a solid frame. I mentioned the overhang above to rule out rainwater and in any case it hasn't rained for the past month. I chose an engineered door as I was advised this was the best option, with an oak finish for toughness. We have to paint the door dark grey or black because of planning restrictions. The door construction seems to be a 40mm thick particle board core with 2mm of veneer front and back and 20mm of oak to the perimeter. Although we have had some quite sunny afternoons, the highest temperature has only been in the high twentys. The Frame was hand made by others. I'm not really in any doubt that the heat from the sun is causing the door to warp as a result of some kind of differential expansion. The problem is that the supplier is blaming the paint system, suggesting that its UV causing the bow. I need to debunk this argument and get a refund so I can buy another door, probably a solid timber one. John Link to comment Share on other sites More sharing options...
iNow Posted June 21, 2018 Share Posted June 21, 2018 Materials breath. Thermal expansion will occur regardless of coating and regardless of construction quality. If it were just a UV issue, you could throw a few costs of Epifanes on it and call it a day Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted June 21, 2018 Share Posted June 21, 2018 3 hours ago, studiot said: You have mentioned a warping of 6mm which suggests you are in a metric country, ie not North America. It might suggest Burma, Liberia or USA... http://mentalfloss.com/article/55895/countries-havent-adopted-metric-system On Topic. UV degradation is a permanent affect. It doesn't go away at night. Link to comment Share on other sites More sharing options...
studiot Posted June 21, 2018 Share Posted June 21, 2018 9 hours ago, John Jeffkins said: STUDIOT thanks for your interest. I am in South East England. The door warps along its length, it bows in, which is counter intuitive. The door was fitted by a professional, with three100mm hinges, fixed securely to a solid frame. I mentioned the overhang above to rule out rainwater and in any case it hasn't rained for the past month. I chose an engineered door as I was advised this was the best option, with an oak finish for toughness. We have to paint the door dark grey or black because of planning restrictions. The door construction seems to be a 40mm thick particle board core with 2mm of veneer front and back and 20mm of oak to the perimeter. Although we have had some quite sunny afternoons, the highest temperature has only been in the high twentys. The Frame was hand made by others. I'm not really in any doubt that the heat from the sun is causing the door to warp as a result of some kind of differential expansion. The problem is that the supplier is blaming the paint system, suggesting that its UV causing the bow. I need to debunk this argument and get a refund so I can buy another door, probably a solid timber one. John Thank you for this better description. My comments are as follows. 9 hours ago, John Jeffkins said: The door warps along its length, it bows in, which is counter intuitive. This is not suprising and quite consistent with the other statements. Firstly the door presumably opens inwards and has some sort of threshold and framing stops which would prevent it moving outwards. So why does it move inwards and why the bottom not the top? Well the top part of the door will be at least partly shaded by any porch or overhang etc. So the bottom half will receive more sunshine. Obviously the outside is heated much more by the sunshine compared to the inside so will try to expand. This will cause the outside to lengthen, compared to the inside and the door will then curl under, rather like a bimetal strip in a thermostat. I can't be persuaded that paint and or veneer finishes have significant effect on piece of 40mm thick particle board, it must be that which is bending. Can you erect a temporary shade for the lower part to test if the door doesn't then curl under? We are expecting another week of warm weather. You could even remove some or all of the grey paint and show that it still happens with this door. Proof positive that it is the door not the paint. There is an known effect where if you only paint one side of a lightweight door, the skin tension of the paint can cause the door to bow, but that would be in the opposite direction. Perhaps the manufacturer is pinning his hopes on that? It certainly does sound (On the face of it ) as though that door is not suitable for that location. As regards temperature, my front door faces due south and on a 20oC day the door itself can reach over 30oC on the outside. Link to comment Share on other sites More sharing options...
swansont Posted June 21, 2018 Share Posted June 21, 2018 9 hours ago, J.C.MacSwell said: It might suggest Burma, Liberia or USA... http://mentalfloss.com/article/55895/countries-havent-adopted-metric-system i.e. not one of the backward countries. 48 minutes ago, studiot said: As regards temperature, my front door faces due south and on a 20oC day the door itself can reach over 30oC on the outside. This is an important point. Direct sunlight will get things warmer than the ambient temperature. You could also test if it is thermal if you had a portable heater, which you could place near the door. Something that is red-hot (filaments of a heater) will have even less UV than sunlight. Link to comment Share on other sites More sharing options...
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