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Green Building Bible, Fourth Edition
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  1.  
    I am trying to decide how many windows I should specify for my new workshop.

    It is being built to the spirit (if not the actual letter) of the Passivhaus standards - certainly for the floor, walls and roof anyway.

    Compromises may be forced on me for reasons of cost when it comes to the glazing.

    It is a 52 sq. m. (8m x 6.5m) single space with a dual aspect roof, oriented north-south for solar purpose, the southern elevation of which is dedicated to the future installation of solar (PV and hot water).

    The northern roof elevation will have between 3.7 and 6.5 sq. m. (effective daylight area) of Velux windows with obscured glass (for privacy due to the 14 storey tower block to the north!). (The final figure will be decided upon after further consultations with my structural engineer.)

    The 8m front (due south) wall can accommodate a 2.4m x 1.2m window. Space restrictions due to various doors prevent more here, and anyway I don't really want a lot of glazing on the southern aspect of a space insulated to Passivhaus standards.

    On the 6.5m western aspect I am contemplating two 2.4m x 1.4m windows.

    And on the eastern wall, one 2.4m x 1.2m window.

    Again, for reasons of privacy there is no glazing in the north wall.

    Leaving aside any discussion about the insulation values of the windows (as this is something I feel I am reasonably well across) my concern is will I get enough light into the building to facilitate fine work without having to wear my reading glasses all the time?

    I am not getting any younger and I find, to my immense frustration, that I cannot see things at all clearly unless the lighting is very good. Indeed, sometimes reading glasses alone are not sufficient and I have to resort to supplementing them with expensive head-worn additional magnification, which in turn leads me to be trying to solder things three inches from the end of my nose! (I exaggerate slightly, but you get the picture.) This is not a problem with my eyes per se as I have had them checked and the issue is simply one of the normal changes that one has to endure as a result of creeping age. I am struck by a statistic that I became aware of recently that stated by the time one gets to 60 years old only 25% of the light falling on the front of the eye reaches the retinue at the back compared to that which a 25 year old enjoys.

    I have found it extraordinarily difficult (impossible in fact to date) to turn up any guidelines for necessary and appropriate illumination within something such as a workshop. There are one or two guidelines for habitable rooms within dwellings, but I am pretty certain that this will not do for my situation.

    What does the team think?

    How many square metres of glazing is enough?

    Leaving aside issues of solar gain, can one have too much glazing?

    The object of the exercise is to be able to rely on natural light from the sun for as much of the day as possible.

    Ideally, I am looking to get some kind of empirical feel for what would provide a decent result rather than have to get involved in what would appear to be some very complex calculations otherwise.
    •  
      CommentAuthordjh
    • CommentTimeOct 23rd 2018 edited
     
    Posted By: ealingbadgerI don't really want a lot of glazing on the southern aspect of a space insulated to Passivhaus standards.

    The south wall is the best place for glazing in Passivhaus, with suitable shading to block out summer sun.

    Roofs are bad because of heat loss, east and west walls are tricky because of difficulty of controlling low-aspect sunlight.

    In short, you're probably going to have to ignore guidelines. As ever, PHPP will give you some idea of what to expect.

    BTW, 'daylight' lights (i.e. fluorescent or LEDs with 6500 K colour temperature) mix pretty well if you have them on whilst there is still daylight coming through the windows. I suffer similar symptoms to you, including the difficulty of soldering.
  2.  
    Posted By: ealingbadgerI am not getting any younger and I find, to my immense frustration, that I cannot see things at all clearly unless the lighting is very good. Indeed, sometimes reading glasses alone are not sufficient and I have to resort to supplementing them with expensive head-worn additional magnification, which in turn leads me to be trying to solder things three inches from the end of my nose! (I exaggerate slightly, but you get the picture.)

    Hmm - me too, I have 'age appropriate' eye sight (and hearing) and it is a nuisance. (although sometimes it can be useful not to hear SWMBO :devil::devil:)
    Otherwise wot djh said
    I would go with the planned windows on the south and the west (afternoon / evening light) and forget the rest. After that install quality overhead lighting, fluorescent tubes on the ceiling with adjustable task tights at about 4000k colour at work benches. I would forget about the roof lights, they are expensive to buy and loose too much heat. IMO you won't be able to get enough natural light to do fine/delicate work and even if you could you have to provision for cloudy days. If its lots of soldering then an extract fan is useful, I use one that I can duct to the work station when I am doing tiffany glass - and get an extract fan that has a positive closer.
    • CommentAuthorowlman
    • CommentTimeOct 23rd 2018 edited
     
    Peter_in_Hungary,
    Hmm - me too, I have 'age appropriate' eye sight (and hearing) and it is a nuisance. (although sometimes it can be useful not to hear SWMBO :devil::devil:)

    It's called selective hearing, Peter:wink:
    • CommentAuthorowlman
    • CommentTimeOct 23rd 2018
     
    What is the workshop for?
  3.  
    Many thanks for all the comments so far.

    The workshop is for me to pursue my hobbies in during retirement. These include designing, building and maintaining PA and lighting systems (and other music related electronic gadgetry and instruments), other general electronics, general DIY tasks, wood turning, the manufacture of wooden toys for my grandchildren, other general wood butchery, and I hope to build the new kitchen for the house in there as well.

    I appreciate that a Passivhaus would normally major on south facing windows, but this is in order to deliberately collect the solar radiation for heating purposes. I am not particularly concerned about this. In fact, I am more concerned about having to manage too much solar gain. I do not anticipate having trouble keeping the building warm enough - quite the contrary in fact. I am in West London - hardly the tropics, but we do benefit from a surprisingly mild local climate for the most part. In any event, physical limitations mean that the south wall cannot accommodate more than the single 2.4m x 1.2m window anyway.

    [The supplier of the insulation system that the slab sits in has stated that in his general experience the problems with most of the projects he has been involved in have been overheating - leading to people having to keep the windows open all the time. Now obviously, whether one sees this as a 'problem' or not is very much a question of perspective. :-) ]

    I do plan to employ 6500K lighting as required for the gloomy days (and nights of course) but would prefer as much natural light as I can reasonably accommodate with glazing before needing to use them.

    What kind of percentage of wall space do people have as windows in their personal workshops and would you prefer more (or less)?
    • CommentAuthorowlman
    • CommentTimeOct 23rd 2018
     
    I seem to remember, for colour rendition, probably not a problem for you, artists prefer North light. That's not to say you can't follow suit with some point of use artificial task lighting for intricate tasks. The roof lights will also help.
    Although the strobe effect from fluorescent lighting on rotating machinery may have been eliminated with modern luminaires, it's worth being aware of.
  4.  
    For lighting a long room, several small windows are more effective than one or two big ones, and probably cheaper and more energy efficient. We know this in retrospect. Big windows are all about views.

    Roof windows gather (subjectively) twice as much light for the same area as wall windows.

    Could you light just one area for your work bench(es) and have less light in other areas where you will store stuff?
  5.  
    Posted By: ealingbadgerWhat kind of percentage of wall space do people have as windows in their personal workshops and would you prefer more (or less)?

    My workshop is 4.75m x 5.5m and has 2 windows or 1.8m x 0.9m facing SW (on the short side). the layout is a central work table with, around the periphery a table and full length (5.5) bench with sink at one end. The remainder of the walls are storage. The central work table and bench are standing height. The use is - everything - from stained glass work to welding and repairing farm machinery with electrical and wood work thrown in.

    Is it enough window, only if you are doing something under the window. In practice I go into the workshop and automatically switch on the main light. The lighting is fluorescent tubes, 2 over the central work table (the main light) with a further 3 around the periphery (over the table and bench) These are supplemented by adjustable / moveable task lights.

    As said above with advancing years artificial / supplementary lighting is becoming more important.
  6.  
    Thanks Peter - it is very useful to have a practical example of somebody's reality.

    Has anybody got any observations on the view that building control is likely to take re the amount of glazing - especially in the roof?

    Not including the windows my 'U' Values (fabric only and bearing in mind that this is a non-domestic building) are:

    floor 0.13
    walls 0.15
    roof 0.14

    Only the floor slab is down at the moment and I can (and very well may) beef up the roof number to match the very latest domestic requirement for a 'U' Value of 0.11 W/m2K as, long term, this building may end up being converted into a granny annex.
  7.  
    Don't know what applies where you are, but in Scotland the Building Standards tech handbook requires (for dwellings, not workshops) that the glazed area is at least 1/15 of the floor area.
    • CommentAuthorJamster
    • CommentTimeOct 24th 2018
     
    Just a thought - in my (limited) experience velux aren't cheap... If you are thinking a significant spend on velux, what about simplifying your roof construction, spending the savings on PV earlier on and as above, good quality a) space and b) close-up lighting? Is obscured, N facing glass going to contribute much to 'detailed' lighting?
  8.  
    Posted By: ealingbadgerlong term, this building may end up being converted into a granny annex.

    If it is greater than 40% chance of conversion to a granny annex then I would put in windows to suit that conversion (and drains, water and power) now because it is the easiest and cheapest time to do it and manage the workshop lighting with good artificial lights which in any event are gong to be significantly cheaper than windows (which may get changed anyway) and modern lights are peanuts to run.

    Wot Jamster said +1
  9.  
    The necessary under slab infrastructure (gas, water, soil, electricity, comms, etc.) is already in place.

    I am now giving serious thought to whether obscured north facing roof lights are going to be helpful or not.
    • CommentAuthormike7
    • CommentTimeOct 24th 2018
     
    If the ground outside beneath your windows is light in colour you'll get a bit more daylight in. Snow does this well - or if not always available, any light-reflective surface will help. Maybe park your collection of retired washing machines or other white goods outside. Lovely.

    I have a seriously gloomy workshop and endure continuing guilt and shame that I have not yet sorted it, relying on ad hoc spot lighting to get by, and using several sometimes to minimise shadow.
    •  
      CommentAuthordjh
    • CommentTimeOct 24th 2018
     
    Posted By: mike7relying on ad hoc spot lighting to get by, and using several sometimes to minimise shadow.

    Yes, multiple lights are always good - reduces shadows and doesn't leave you inthe dark if one lamp blows. Fluorescent tubes or LED panels help with reducing shadows.
  10.  
    Posted By: ealingbadgerI am now giving serious thought to whether obscured north facing roof lights are going to be helpful or not.

    Obviously they will help, if only that they will let in some light but IMO not good value for money especially considering the potential conversion. IMO much better to go with LEDs or fluorescent tubes. (T8 fluorescent tubes will be up to 100 lumens/watt which is equivalent to the best leds (at the moment))
    •  
      CommentAuthordjh
    • CommentTimeOct 25th 2018
     
    Posted By: Peter_in_HungaryT8 fluorescent tubes will be up to 100 lumens/watt

    The main thing is to get triphosphor tubes using electronic (high-frequency) ballasts. Either T5 or T8.
    • CommentAuthorvord
    • CommentTimeOct 25th 2018
     
    My current workshop has no windows at all which is just depressing. But even in the new workshop about the same size as yours with two large east facing picture windows I would still expect to turn the lights on when I go in.

    I've never managed to get the right natural light in a workshop. You need the light all around. LED lighting is way cheaper than heating, but some natural light is important for beauty and sanity. I would go pretty and private looking from inside and outside for natural light and fill in the gaps with artificial light.
  11.  
    After input from SWMBO the skylights stay. :-)

    I confess that I am quite comfortable with this as a way forward myself. I just needed a nudge to overcome my indecision on this point.

    The balance is formed of one 2400 x 600 window on the eastern wall, two 2400 x 600 windows on the western wall, and one 1800 x 600 window on the southern wall where doors and other restrictions prevent anything bigger.

    I have forwarded these details to my structural engineer so that he can do the calcs for support of the roof and so forth.

    I was going to install some anyway of course, but based on everybody's input it looks like artificial lighting is going to be a necessity anyway for close work regardless.

    ps - Mike7 - how did you know I had a collection of old washing machines? :bigsmile:
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