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General: Thermal break door

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  1.  
    Any thoughts/comments, obvious failings, on my proposed insulated external door.
    External grade 30 min solid core fire door. The door blank comprising solid timber core faced with 5mm veneer, approx 55mm thick in total. On the inner face apply a 25mm x 20mm deep timber frame,(possibly wider on hinge edge), within the recess created apply a layer of 20mm Aerogel. Face with thin as possible ply, mdf.
    • CommentAuthortony
    • CommentTimeDec 4th 2011
     
    expensive!! thermal bridge round the edges, what will be the U value? thin ply might bend/warp etc?
  3.  
    Not sure what the alternatives are. Are you concerned the expense is in the door or Aerogel. The basic fire door blank is what we will use irrespective of any modifications and the cost of this has been allowed for. The thermal bridge seem unavoidable unless we use a rigid insulation and we are then involved in greater depth. I was thinking that the bridging occurred relative to the door stop and would be therefore somewhat mitigated. The facing ply is my main concern and I am unhappy with this element. Thanks for the comments
    • CommentAuthortony
    • CommentTimeDec 4th 2011
     
    is there a problem with a thicker door? could you make a frame to accept a thicker door, this is what I did.
  5.  
    Hi Tony, do you mean thicker in the sense of a solid timber door, allowing the timber to provide a greater thermal break or thicker so that a more conventional insulation can be applied and presumably then faced. Has anyone else any experience of constructing or purchasing an insulated door?
    • CommentAuthortony
    • CommentTimeDec 5th 2011
     
    Thicker in terms of your door plus a good bit of insulation say 50mm PIR

    It has to have a good frame round the edge

    Doors in Germany and Austria are often almost 120mm thick on good new houses
  7.  
    Thanks Tony, will look at some european examples for detailing etc. Thanks for imput
    •  
      CommentAuthordjh
    • CommentTimeDec 5th 2011
     
    Posted By: Cav8andrewAny thoughts/comments, obvious failings, on my proposed insulated external door. External grade 30 min solid core fire door.

    Is it supposed to be a fire door when installed? If so, I believe you're not allowed to modify the door except as specced/agreed by the manufacturer if you want it to keep its fire rating. Otherwise, it would presumably need testing (which would require a second door to burn?)

    Also, if you or Tony have any URLs of thick European doors to share, that would be interesting.
  9.  
    There are quite a few manufacturers of PassivHaus doors out there (Internorm, Optiwin, Greensteps, Green Building Store to name a few) but they are stunningly expensive.

    Others do non-certified but high performance doors - Hormann, Silverlux etc.

    Rather bizarrely I've found that it is significantly cheaper ( as much as 5x) to use a PassivHaus certified window (some manufacturers offer door variants of their PassivHaus windows, not just a window being used as a door) compared to a PassivHaus certified "door".

    We will be using one for our utility door, although it's been vetoed for the front door on aesthetic grounds (even a frosted version) by SWMBO.
    •  
      CommentAuthorjoe90
    • CommentTimeDec 5th 2011
     
    Having always been an avid DIP (do it properly!) person I am interested how a low U value door could be constructed as per this thread, The manufacturers dont tend to give diagrams how theirs are constructed so come on guys and dolls lets see if we can have a consensus on what makes a good insulated door that we can make ourselves or get made locally for a reasonable price.
  11.  
    Hi, thanks for the comments. Djh, The door is not actually required to be a fire door but in my limited experience they tend to be amongst the strongest constructed flush doors. In theory any solid core (timber not composite) door blank would be suitable. Also needs to be 1m wide and a fire door seems to be more readily available in wider widths presumably for commercial use. It is though a really relevant comment and has made me think I will need to maintain a high degree of fire resistance which seems only sensible, as it is a means of escape, if not exclusively so. Mark, thanks for the manufacturer details, will look them up if only for information (because of cost). This price factor was my fear but really don't want to go down the glazed route which judging by your comments on pricing is a shame. Incredible to think there is such a hike in price for a 'door' door.
  12.  
    joe, it seems to me a project just waiting to happen. Has all the hallmarks of a doable task.
    •  
      CommentAuthorjoe90
    • CommentTimeDec 5th 2011
     
    I noticed when in Austria a few years ago that their doors (internal anyway but didnt notice the external) didnt fit totally within the frame but had a say 15mm flange that extended over the frame on the inside. If you were restricted to a "normal" frame you could increase the thickness of the door in this way and the flange would give you an additional place to fit seals. (I'm off to see if I can use google sketchup to offer my penn'eth worth)
  14.  
    You could use an over-sized sheet of ply on the inside, this could partly cover the frame and give you a place to fit secondary seals, you could router lines in the ply to create a T&G effect and spray-paint it.
  15.  
    Have seen similar doors across in Switzerland, could give a double lap which and as you say could work with pre-existing doors. Have been thinking, don't most European external doors tend to open outwards whereas ours open inwards. This will have a bearing on the construction required on the hinged edge of the door. If insulation is placed on the inner face (as proposed) would need to make allowance for sufficient timber into which to locate hinge. If the European model was followed this would not be an issue as you would still be locating hinges into main body of door. Mind you if you extended edge detail was adopted in that situation there would be the minor issue of the impossibility of opening the door!
    •  
      CommentAuthorjoe90
    • CommentTimeDec 5th 2011
     
    Viking House

    Great minds think alike
  17.  
    Nice one joe! You could use a dog-leg hinge Andrew. How much is the Aerogel for a door?
    • CommentAuthorowlman
    • CommentTimeDec 5th 2011
     
    You're right Andrew, most Continental doors are double rebated, certainly in Germany and Austria. This gives much more scope for joinery weather seals. The frames are often of steel too which provides a movement free housing. Not sure how they reconcile that with thermal bridging though. I made a solid Oak door for a client up in the windy Yorks Dales with a double rebate and 25mm of kingspan inside, with oak T&G front and back and a DG small window. It ended up nearly 3" thick and weighed a bloody ton fortunately the frame was made to suit it. I'd be tempted to get the frame right first even if it means ripping the old one out, if the frame and fixings are flimsy you could end up with problems. You can design a new frame complete with seals around your modified standard door.
  19.  
    Viking, Not checked Aerogel costs yet but was thinking this was a reasonable use of the material as the m2 is small.
    Not heard of a dog leg hinge is this what I know as a parliament hinge?
    • CommentAuthorqeipl
    • CommentTimeDec 5th 2011
     
    I built two exterior doors for my house.
    25mm PUR core with 25x30 softwood perimeter
    12mm plywood faces with 12x48 hardwood edging.
    All bonded and sealed with epoxy resin.
    Finished with high quality yacht paint.
    U-value of PUR cored panel c.0.8 (a bit more around the solid perimeter).

    One door opens into an unheated lobby (best practice).
    The other into a utility room with thermostat set at 15C.

    Hope that helps.
  21.  
    owlman, did your door open outwards or inwards? Would definitely be constructing a specific heavy duty/stable frame to match, probably with 4 no. heavy duty hinges and as you say work out a robust seal detail. Did you have any issues with the gap required between door edge and frame on the opening edge. I constructed a front door for a previous project (internal, in a lobby) which was approx 75mm thick and we had binding on the door as it opened (had to chamfer the leading edge or create a wider gap) but I guess that would only happen if the double rebate detail was not used.
  22.  
    qeipl, thanks for door details, this really helps, goes for all the input received, thanks
    • CommentAuthortony
    • CommentTimeDec 5th 2011
     
    half way through making the outside of mine
    • CommentAuthorowlman
    • CommentTimeDec 5th 2011 edited
     
    Hi Andrew
    With such a thick door getting the "leading edge" of the door right as it strikes the frame did require a bit of thought. The door opened inwards, that's what the clients wanted. As for hinges I used four heavy duty stainless ones, 3mm thick leaves, but at one stage I was going to use continuous hinge, like a heavy duty piano hinge.
    •  
      CommentAuthorjoe90
    • CommentTimeDec 5th 2011
     
    Cav8andrew,

    Parliament hinges are deeper than normal (hing pin away from the door)to allow a door to hinge back on itself and not foul the architrave for example.
    http://www.screwfix.com/p/parliament-hinge-satin-chrome-102-x-125mm-pack-of-2/68952
    Dogleg hinges have a 90' bend in the leaves to allow hinges to fit around ply on the face of the door.
    http://www.toolstation.com/shop/Hardware/Hinges/Stormproof%20Hinge/d170/sd2270/p92741
    • CommentAuthortony
    • CommentTimeDec 5th 2011
     
    but they throw the door too near to the closing jamb and are not very suitable for thick outside doors
    • CommentAuthorwookey
    • CommentTimeDec 6th 2011 edited
     
    Chepest way to get good U-value doors is Garage doors (normal-sized, not the big front ones). Hormann do one which is U=0.43 (centre) for foam core in steel case. Overall door U is 1.3. Next best (2 years ago) was IG doors with GRP facings over foam core).

    Mark Bennett - you might be interested to know that frosting a DG unit reduces it's U sugnificantly (according to Greensteps). so nominal 0.6 3G goes down to about 1.0-1.1 if one pane is frosted. Seems to be a well-kept secret.

    Now that new-build need U=1.4, I'd expect such doors to be available reasonably cheaply.
  28.  
    owlman, what was the bit of thought required? modification of the leading edge, slightly wider gap to frame or some other fiendish detail. We eventually put a slight chamfer on ours.
    joe and tony, re. the parliament hinge, have used these on restoration projects (exactly as you describe joe) and aware of the issues of throw but the term dog-leg hinge was not one I recognised and wondered if they were one and the same so thanks for the description. Nice looking door Tony, are they engineered boards?
    wookey, thanks for door info, was it explained why frosting reduced its U value? Worth knowing as the effect seems significant.
    • CommentAuthortony
    • CommentTimeDec 6th 2011
     
    left over engineered flooring -- yes
    • CommentAuthorwookey
    • CommentTimeDec 6th 2011 edited
     
    Re frosting: not in any useful detail, no -I asked that too. "Something to do with the way the reflections work". You can see that the frosted layer diffuses the light, and the coatings work because the sunlight comes in at one frequency and room IR goes out at another. A layer which deflects the rays could clearly have an effect on this process, but I'd very much like to have the effect confirmed by someone else who knows about the sordid details of glazing coatings. (Greensteps run their own glazing unit factory which is why they have detailed knowledge in this area).

    One theory would be that light is deflected beyond the critical angle of the next sheet so it bounces about a bit before getting through, and thus some hits the coatings going in the wrong direction.

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