Acoustic treatment of a Substation conversion with a Cinema

Discussion in 'Home Cinema Buying & Building' started by WSquared, Aug 1, 2012.

  1. WSquared

    WSquared
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    Hi all
    We recently purchased a former electricity substation building next door which was built in the 1930s in the style of a Tudor cottage. It is a very industrial construction, which makes the conversion a challenge. To meet building regs that is.

    The walls are 13.5" (340mm) solid; three bricks thick. The building is detached. I am not bothered about sound proofing; merely acoustically improving the room at the same time as thermally insulating it to meet current building regs. I looked at the option of thermally insulating externally, but with the mock Tudor timbers, it would be challenging and generally much more expensive.

    The building is big enough for the ground floor to become a garage and workshop once the old 'slab' is removed and a new one created lower down, and also for the newly created first floor to be split into a cinema and home office/guest room.

    Depending on how I insulate, each upstairs room will be about 4.9m x 4m, with the cinema to be 2.7m high, but not a uniform height. (Back room will be vaulted.)

    I have attached a pics with some extracts of the plans to set the scene better.

    There is about 25tons of concrete to come out... :eek: and a bunch of steel to go back in.

    I have two main options for insulating them internally in order to meet building regs, while also trying to maximise room space.

    Basic (similar) examples of the two options are attached.

    Options:
    1) using horizontal 38x25 batten mounted on wall (with felt spacer on wall) + multifoil insulation (TriIso10 or Thinsulex TLX Silver) + vertical 38x25 batten + (possible green glue) + plasterboard + (possibly green glue) + acoustic plasterboard

    - Pros: This eats only about 85mm of the room space; theoretically better thermal performance than option 2
    - Con: I am wary about the acoustic performance, but hopefully the green glue and acoustic plasterboard would fix it well enough

    2) PIR/PUR rigid board (eg celotex) straight on wall, approx 70mm (TBD- building regs) + 38x25 batten (fixed through the PIR into the wall) + (possibly green glue) plasterboard + (possibly green glue) + acoustic plasterboard

    Pro: I am more comfortable that the acoustic performance will be ok
    Con: This eats about 125mm of the room space, but the thermal performance may not be quite as good (theoretically)
    (option 2 can have a 25mm layer of 'acoustic' mineral wool insulation between the battens; at a higher cost of course)


    The builders seem to think that the two options (including materials and time) will cost vaguely similar prices as each other.

    I would be keen to hear your thoughts as I have to put this into the building reg drawings very soon. Note that other first floor room (home office/guest room) will use the multifoil option to maximise room space. My design person will probably not be over to moon about more drawings to specify different things for the front and back rooms, but the acoustics are obviously important to me.:D

    As part of the 'decoration' of the room, I plan to incorporate some acoustic panels in appropriate places; possibly made by myself, possibly not.

    And before you say it, yes I have thoughts about going with in-wall Ci speakers, but I am going to have to make due with my current kit for a while; as this is going to cost a lot more than I expected. :(

    Oh, and I have a nice new clean power feed from the not-so-nice new substation pod installed in front of the building fronting the pavement. Just 8 meters of power cable from transformer to my meter.

    cheerios,
    William
     

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    Last edited: Aug 2, 2012
  2. Trollslayer

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    A lot of work but an incredible property.
    Be warned - it will probably be built with engineering bricks which can be very difficult to drill through.
     
  3. inzaman

    inzaman
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    Let's just try this thread in this section of the forums :)
     
  4. WSquared

    WSquared
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    Luckily, it is built with standard bricks. While they are quite solid ones, they aren't as dense as engineering bricks.

    Here are a few pics of the place as it is at the moment, including the roof structure. It's a bit of a shame to have to dismantle the elegant timber structure of the existing roof, but is has to be done. They are in great condition and dead straight, so we plan to re-use some of the beams to make features of them in the rear office/guest-room which will have a vaulted ceiling. We'll use them for the collars/rafter-ties about every third rafter. It's a bit romantic to use them as a structural element (albeit a minor one) in the new design... And I'll use the rest for some other DIY project.

    Note that the dust covered 'floor' is a concrete slab which needs to come out as well...
     

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  5. WSquared

    WSquared
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    perhaps I didn't put an interesting enough title on this post...
     
  6. bighairybloke

    bighairybloke
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    I would use polystrene backed plaster board on all walls to meet BR, then add acoustic treatment afterwards as needed. Cant see the need for green glue, your walls are thick enough...your not gonna be bothering your neighbours much through them....also, AIUI, acoustic plasterboard acts as a sound proofer, not as an acoustic treatment ie improving the sound in the room.

    Smashing project and building, love a building with character!

    Shame the room is so close to being square, but at least it isnt dead on square! Id also consider an IB subwoofer system venting into your games room;-)

    Steve
     
    Last edited: Aug 6, 2012
  7. WSquared

    WSquared
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    Thanks Steve. I was beginning to think I was not going to get any views and would have to ask the question a different way in a new thread.

    Due to the way the new structure is designed with vertical steel posts hidden in the partition wall, I can't really change the location of that wall to adjust the ratio of the L x W. I did look at the 'ideal' acoustic room ratios, but in addition to L x W, the height ratio is included and doesn't really fit with my room; or very many British-sized rooms I would imagine.

    I could artificially build the walls thicker using different thermal insulation techniques, which I am considering as part of this thermal/acoustic dilemma.

    Apparently polystyrene backed plasterboard doesn't 'practically meet the building regs that came in to force in 2010. They would have to be insanely thick.

    I'm not trying to sound proof the room anyway, just make it behave better from an acoustic perspective.

    I'm thinking I will make a feature out of some acoustic panels. In the June 2011 HCC, I found a pic of tall acoustic panels (and some neutral panels) arranged in sizes and spacing apparently representing the Fibonacci sequence. I like the look anyway...

    I have read a couple of the IB threads, but I would have to mount the housing in the adjacent room and vent it through the partition wall. I could not put it below the room, in the garage space, due to building fire regulations as the space below is a garage/workshop; ie not habited. It has to all be fire resistant, so it will be line with 'fireboard' to keep the thickness down. I haven't had time to investigate IB enough to see if others have mounted in adjacent rooms, but I would be wary of somebody mucking about with it in the other room; ie my 6 year old or his friends as they get older...

    But I do like the idea. If I can work out a way to sensibly fit it in, I may just have a go!:smashin:
     
    Last edited: Aug 7, 2012
  8. bighairybloke

    bighairybloke
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    The polystyrene(or similar stuff used on kingspan) backed plaster board will be better than that over rated tri iso stuff that's for sure, but you need advice from the building reg people. Ask for the thinnest solution that meets the regs. I would have thought 100mm of insulation would sort it. Then treat the room with absorbent panels where needed. A nice thick carpet with a real thick underlay too. Heavy curtains will help.

    If you can do an IB defo go for it!

    Steve
     
  9. WSquared

    WSquared
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    I thought about the PIR/PUR backed plasterboard, but running cables requires chasing out the insulation from the back side. And you have to get it right first time and not change it.
    That's why I was looking at the PIR board fixed on with battens then plasterboard mounted to the batten. Gives a 25mm void for cabling and a bit of acoustic friendly mineral wool.

    Just noticed 'ceiling mounted' IB in your sig. I'll have to have a look at whether that could work for me. Not sure as the ceiling/small roof space will be quite limit ad and challenging; which may put the vent location in a suboptimal place.
     

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