Archiesgrandad Posted September 29, 2015 Share Posted September 29, 2015 I have just read the report in MMM on the new Itineo SB 700, and contained in the facts and figures at the end was the information that the walls are 30mm thick, the roof is 32mm thick, and the floor is 50mm thick. To me it seems that they have got it wrong. I was taught that warm air will rise and cold air will sink, so if I was designing a new motorhome I would make the roof thicker than the walls or floor, because I would be more concerned to keep in the hot air in, and I would be less concerned that cold air might rise under the van and come in through the floor. Why do they do it? AGD Link to comment Share on other sites More sharing options...
Mike B. Posted September 29, 2015 Share Posted September 29, 2015 Well No i can't! Link to comment Share on other sites More sharing options...
Tracker Posted September 29, 2015 Share Posted September 29, 2015 My mind has gone blank too! Link to comment Share on other sites More sharing options...
AndrewJo Posted September 29, 2015 Share Posted September 29, 2015 It's not insulation It's the loading the floor needs to carry more weight Link to comment Share on other sites More sharing options...
Brian Kirby Posted September 29, 2015 Share Posted September 29, 2015 Which is to say, the floor needs to be thicker than the walls or the roof for structural reasons, and the resulting spaces are then filled with insulation. So, it's just a bonus to your tootsies (which create the need for the strength in the first place). The natural symmetry of the world is truly wonderful to behold! :-D Link to comment Share on other sites More sharing options...
Archiesgrandad Posted September 30, 2015 Author Share Posted September 30, 2015 OK, I can see the point about,increasing the thickness to improve the stiffness of the floor, when I was young and foolish I built 2 glassfibre sailing boats and know quite a lot about foam sandwich construction, but I'm not sure I would choose it for the rough and ready construction of the underneath of a road vehicle, but these manufacturers make more money than I ever did, so it must at least be acceptable to the folk who buy them. As they presumably use the same technique for the sides and roof, substituting aluminium foil for the outside and heavy duty vinyl wallpaper for the inside instead of thin plywood, is it reasonable to think of the foam fillers as insulation at all. Just over an inch of foam would hardly qualify as adequate heat insulation, in our stone built house we have 12 inches of insulation in the loft, and the walls of the new extension are made from 9 inch thick insulation block, with 4 inches of foam, and we don't intend to take our house to anywhere cold. Just a point for Brian, the extra thickness in the floor will prevent the cold air passing it's coldness through the floor, and also prevent any warmer air that might be under the van from passing it's warmth inside. Therefore, all the coldest air inside the van will remain on the floor, and your feet will be colder. I still think the roof should be thicker than the floor. AGD Link to comment Share on other sites More sharing options...
Basil Posted September 30, 2015 Share Posted September 30, 2015 But the insulation quality of the material used has little bearing on the thickness. My brother has recently built rooms into the roof of his property and the insulation material was a seven layered flexible sheet that was only around 2 to 3 mm thick and purchased in rolls, at around £135 per roll by the way, but far exceeded the required thermal efficiency as laid down in the building regulations and as such passed building inspection. This was literally against the underside of a tiled roof and before being plaster boarded and plastered. Our own new panel van uses 'Thinsulate' insulation and is perfectly cosy so far, will determine after we have used it through the winter but it has passed the standards for all season use according to the literature. Bas Link to comment Share on other sites More sharing options...
Derek Uzzell Posted October 2, 2015 Share Posted October 2, 2015 Archiesgrandad - 2015-09-30 12:33 PM ...I still think the roof should be thicker than the floor. AGD It might be useful to have the ‘thickness' of the space between the motorhome living-area’s ceiling and the underside of the roof’s outer skin greater than the ’thickness’ of the space between the upper and lower surfaces of the floor if warm-air ducting, water pipes, electrical cabling, etc. were normally run through the ceiling-to-roof space - but they aren’t. As Brian points out, the floor is a structural component and (in the case of coachbuilt motorhomes) is often bonded to the chassis as well as bolted to it. To provide the necessary stiffness the floor needs to be stiff (hence thick) while the roof does not. It is indeed the case that motorhomes tend to be colder at floor level than at ceiling level, but that’s because their heating systems are relatively crude. In any case, even if you had a super-thick roof, you’d still need to ventilate it - otherwise the motorhome’s interior would rapidly become horribly fuggy. Link to comment Share on other sites More sharing options...
colin Posted October 2, 2015 Share Posted October 2, 2015 Archiesgrandad - 2015-09-30 12:33 PM , when I was young and foolish... Just a point for Brian, the extra thickness in the floor will prevent the cold air passing it's coldness through the floor, and also prevent any warmer air that might be under the van from passing it's warmth inside. Therefore, all the coldest air inside the van will remain on the floor, and your feet will be colder. I still think the roof should be thicker than the floor. AGD Things don't change it seems :D If it's, lets say, a air temperature outside of -5 you want to be stopping the warmth inside going out, and that will be throu the floor as well as elsewhere in the construction. On our 'new house' the floors are 350mm thick the walls are 300mm thick, but the thermal insulation of the walls are greater than the floor. Link to comment Share on other sites More sharing options...
Billggski Posted October 2, 2015 Share Posted October 2, 2015 Narrow boats are usually built with 10-6-4 mm steel, and the 10 is on the bottom, the 4mm is the roof, which you usually walk on. Not much insulation in steel though. Link to comment Share on other sites More sharing options...
docted Posted October 3, 2015 Share Posted October 3, 2015 My thoughts, for what they are, could it be for sound deadening to prevent road noise intrusion while traveling. Link to comment Share on other sites More sharing options...
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