Studio build in Wales, UK...again!

Waka wrote:

As an alternative temporary measure, you could add exterior thermal insulation to your roof deck (celotex or something similar) and put felt on top of that. So you would have a warm roof then. As your roof is almost always the biggest problem, this might be good enough in the mean time. Then when you build your outer leaf, just move the celotex to the outer roof deck. If you do this, follow the correct warm-roof design for your area (not sure about wales building regs). You will probably need to replace your felt with a vapour control layer. Dan

Thanks so much Dan, I'm thinking that during the cold wet months we've had recently the moisture from the inside has been collecting up there and being absorbed into the OSB and staying there due to the roof being covered in felt. Now that we're having warm weather the sun is beating down drying it out and causing it to drip down into the room.... does that make sense? Is that how physics works? Regarding the warm roof idea, I agree with you; this was my first thought. I am planning to have a warm roof anyway once I do my outer leaf, and I do have a load of celotex here handy, which is good because every builder's yard in the local area is closed right now due to the lockdown. I better research if celotex is vaporr permeable or not though, because if it's not then surely it will just be making the problem worse? I also can't build my silencer boxes due to the lockdown, but I could just cut some holes where the sleeves of the boxes will go and then put a little shelter on the outside for them? In regards to where the silencer boxes/vents are positioned, would it be better to have them up high or does it not really matter once the fan is in there moving the air? I went up on the roof and couldn't see anything obvious, there are seams but they are all overlapped really well and have a bead of roofing silicone under them, I went ahead and went over some of the seams again anyway just in case. Where I thought I saw a leak is actually in the middle of the roof. Other alternatives I thought of are: Taking out a load of the insulation that I put up, maybe that peak "corner trap" is causing the majority of the problem. Leaving the doors open with a fan inside should temporarily help. I could even cut a ridge vent in and then seal it back up when I do the outer leaf... I wouldn't really be able to cut soffit vents in though, not with out some major operation. Thoughts? Paul

TomVan wrote:

Paul, Hopefully you do not have a roof leak. :shock: In my studio build back in 07 it was very airtight. By the time I had put new lumber (wet), drywall and mud and paint. I ran a dehumidifier for a couple weeks and took out 20 gallons of water. If I would have known this before hand I would have stated drying out earlier. I ran into a problem with moisture building up between the panes of glass. That is when I knew I had a problem. Typical construction usually does a dry out period before and after drywall. Like you have found out, just by leaving the doors open, it is helping. If you can, run heat/propane and fans to help remove the moisture. Hopefully it is that simple and like I said hopefully not a roofing problem. Best T

hi Tom, Thanks a lot for the optimism, it makes sense to me and I really hope you're right.... I do not have any drywall in there at all (so no mud) I did however use a little bit of fresh lumber up in there for my collar ties, it could be adding to the problem for sure. The rest of the timber is treated, so at least it should last despite the condensation for a while. I'll definitely be leaving the doors open and running some fans in there for a week or so, I don't have any heaters unfortunately. Thanks for your advice, I'm glad you were able to get yours sorted in the end! Paul

Paulus87 wrote:

Thanks so much Dan, I'm thinking that during the cold wet months we've had recently the moisture from the inside has been collecting up there and being absorbed into the OSB and staying there due to the roof being covered in felt. Now that we're having warm weather the sun is beating down drying it out and causing it to drip down into the room.... does that make sense? Is that how physics works? Regarding the warm roof idea, I agree with you; this was my first thought. I am planning to have a warm roof anyway once I do my outer leaf, and I do have a load of celotex here handy, which is good because every builder's yard in the local area is closed right now due to the lockdown. I better research if celotex is vaporr permeable or not though, because if it's not then surely it will just be making the problem worse?

Not a problem! That's not how i understand it. Condensation builds up in the room due to perspiration, or because the door was open, letting damp air in and then the door was closed and sealed with nowhere for it to go. It mainly happens in the UK when it's very cold and damp outside. The internal temperature is almost always higher than outside, and when the water vapour in the air meets the cold walls/roof, then it condenses on the surface. This mainly happens during the cold months. Perhaps you have only noticed it recently? Whether the celotex is permeable won't affect it really, as your roof deck will have a vapour barrier on it preventing any water vapour escaping the room anyway. The idea is to keep the water vapour inside the room but at a high enough temperature to remain as vapour and not condense on the surfaces. The celotex makes the roof deck warm enough to prevent the vapour condensing on it (assuming it has a high enough R-Value or thermal resistance). If the vapour never gets cold enough to condense it's not a problem. If you don't have enough passive ventilation it will get warm and stuffy in there though. Make sense? You will still get condensation on your walls/corners I'm afraid though unless you insulate your walls and have a vapour barrier room side of the insulation. Dan

Waka wrote:

Paulus87 wrote:

Thanks so much Dan, I'm thinking that during the cold wet months we've had recently the moisture from the inside has been collecting up there and being absorbed into the OSB and staying there due to the roof being covered in felt. Now that we're having warm weather the sun is beating down drying it out and causing it to drip down into the room.... does that make sense? Is that how physics works? Regarding the warm roof idea, I agree with you; this was my first thought. I am planning to have a warm roof anyway once I do my outer leaf, and I do have a load of celotex here handy, which is good because every builder's yard in the local area is closed right now due to the lockdown. I better research if celotex is vaporr permeable or not though, because if it's not then surely it will just be making the problem worse?

Not a problem! That's not how i understand it. Condensation builds up in the room due to perspiration, or because the door was open, letting damp air in and then the door was closed and sealed with nowhere for it to go. It mainly happens in the UK when it's very cold and damp outside. The internal temperature is almost always higher than outside, and when the water vapour in the air meets the cold walls/roof, then it condenses on the surface. This mainly happens during the cold months. Perhaps you have only noticed it recently? Whether the celotex is permeable won't affect it really, as your roof deck will have a vapour barrier on it preventing any water vapour escaping the room anyway. The idea is to keep the water vapour inside the room but at a high enough temperature to remain as vapour and not condense on the surfaces. The celotex makes the roof deck warm enough to prevent the vapour condensing on it (assuming it has a high enough R-Value or thermal resistance). If the vapour never gets cold enough to condense it's not a problem. If you don't have enough passive ventilation it will get warm and stuffy in there though. Make sense? You will still get condensation on your walls/corners I'm afraid though unless you insulate your walls and have a vapour barrier room side of the insulation. Dan

Okay, that makes senes... So, what if I temporarily install a vapour control layer in front of the insulation (the warm side) Then the vapour won't be able to get up into the insulation/underside of the OSB roof deck. Good idea or terrible idea? Paul

So I do not have enough Celotex to cover the entire roof, and it is the wrong thickness anyway... I also do not have the correct type of vapour control layer... Because I can't currently get any supplies I am thinking I need to do something temporarily to stop the condensation until I can fit a warm roof and do the job properly. So I am thinking of taking down the bulk of the insulation sitting up in the peak which is the hottest part obviously, and then putting in some vents on each gable, as high up as possible. Then when it comes to building the outer leaf in the future I can simply patch the vents up again. My thinking is that without the outer leaf being there my isolation is going to be next to nothing anyway, so I am not really losing anything by compromising this leaf. My real question is do you guys think that by removing this insulation and putting in the two gable vents that will be enough ventilation to prevent condensation? If not then I'll have to do a ridge vent. My thinking is since I do not have drywall on the bottom of the rafters, the bottom of the roof deck is exposed to the inner room, so provided I had fresh air coming into the room by means of another vent on the wall then I wouldn't need soffit vents anymore since the soffit vents would usually be there to provide air flow in the cavity between the roof deck and the ceiling... my ceiling is the roof deck. Thoughts? Paul

It is very difficult getting supplies at the moment. I managed to order a delivery of insulation on ebay though, so you could look on there for your celotex. You could try putting in some vents on each end in the gable. Building regs recommend the equivalent of a continuous 25000mm2 airflow if you don't have ridge vents for a roof cavity, but that's a lot of temporary vents :shock: I would try less vents and maybe just stick a bathroom extractor fan in the wall at the gable. Dan

Waka wrote:

It is very difficult getting supplies at the moment. I managed to order a delivery of insulation on ebay though, so you could look on there for your celotex. You could try putting in some vents on each end in the gable. Building regs recommend the equivalent of a continuous 25000mm2 airflow if you don't have ridge vents for a roof cavity, but that's a lot of temporary vents :shock: I would try less vents and maybe just stick a bathroom extractor fan in the wall at the gable. Dan

My temporary ventilation plan would look like this: I'd remove the insulation from the peak of the ceiling so there is continuous air flow from one side to the other. It's not the ideal solution for many reasons but it would be the quickest to implement and the easiest to patch up once the vents are no longer required. The extractor fan could be a good idea, they are quite small though. When they are not powered on, do they still act as a vent? Do you think that will be enough ventilation to get me by until I can install the warm roof? I'm wondering if it would all be in vain since I am not preventing the air from below inside the room getting to the roof deck? Paul

Brutal! As you know, I had moisture issues in my basement before as well. All of your discussions here are spot on. What is your plan to remove the mold though? Greg

Gregwor wrote:

Brutal! As you know, I had moisture issues in my basement before as well. All of your discussions here are spot on. What is your plan to remove the mold though? Greg

Hey Greg, Yeah moisture has sure been a curse for both of us. It was a silly mistake on my behalf as I stupidly thought that 1. The roof deck would be kept warm if packed with insulation therefore avoiding the chance of condensation and 2. It would be fine for a while until I got my outer leaf built. How wrong I was! Still, sometimes you have to experience something the hard way in order to actually learn. Now I know that the problem was due to air leakage from below up through the insulation, carrying moisture with it up under the roof deck, and the roof deck was not warm enough due to the wrong type of insulation. If I had spray foamed it or used rigid foam insulation sealed with a vapour barrier then it would have worked... but then I wouldn’t have been able to use all that space for thick acoustic treatment. Yesterday I spent the day ripping out all of that bass trapping goodness, which broke my heart because it was such a long horrible job putting it up there!! A lot of it was wet and all of the rafter bays have black mould and compromised caulking. I will clean it all off by bleaching the crap out of it to stop it from spreading. Now I have a question... If I leave the hangers up there with no insulation behind them how effective do you think they will be? I will be having a false ceiling at the height of the lower chord of the trusses (9’) which will basically be a load of fabric frames with insulation behind. This would conceal the hangers behind it. Paul

I will clean it all off by bleaching the crap out of it to stop it from spreading.

My buddy who deals with mold for a living told me to just use dish soap in water to spray on the mold and then use a wire brush to remove the mold. Keep it wet as you scrub it off. Be sure to wear a good mask (like N100 or P100) while doing it -- good lucking finding one right now :-S

If I leave the hangers up there with no insulation behind them how effective do you think they will be?

I'm sure they'll work pretty good but obviously not as well as before :( Those big piles of insulation bring back horrible memories for me. I'm sorry you're having to go through this. You did such a great job. Just one more hurdle here. Soldier on my friend! Greg

Gregwor wrote:

I will clean it all off by bleaching the crap out of it to stop it from spreading.

My buddy who deals with mold for a living told me to just use dish soap in water to spray on the mold and then use a wire brush to remove the mold. Keep it wet as you scrub it off. Be sure to wear a good mask (like N100 or P100) while doing it -- good lucking finding one right now :-S

If I leave the hangers up there with no insulation behind them how effective do you think they will be?

I'm sure they'll work pretty good but obviously not as well as before :( Those big piles of insulation bring back horrible memories for me. I'm sorry you're having to go through this. You did such a great job. Just one more hurdle here. Soldier on my friend! Greg

Nice tip, that will be a much nicer solution for working up there with. I think I'll make the ceiling panels easily removable so that when I don't need the vents anymore I can block them up and then reinstall insulation behind the hangers. Paul

Good tips Greg! Paul, how are you planning on designing your ceiling modules? Running some joists and laying insulation over the top and in between, then stapling fabric to the underside?

Waka wrote:

Good tips Greg! Paul, how are you planning on designing your ceiling modules? Running some joists and laying insulation over the top and in between, then stapling fabric to the underside?

Hey Dan, I've already got some timbers running perpendicular with the side walls onto which I can secure some light weight timber frames with fabric stretched across. Behind the fabric and inserted into the frame will be thick Dacron insulation, which has a GFR of about 3000-4000layls. If more thickness is required then I could put some fluffy behind it too. To stop them sagging I'll put some battens across and some chicken wire or netting if needed. I'll also put some LED downlights into certain panels. So it'll basically be a removable grid of panels instead of one solid permanently fixed drop ceiling. Paul

Waka wrote:

Good tips Greg! Paul, how are you planning on designing your ceiling modules? Running some joists and laying insulation over the top and in between, then stapling fabric to the underside?

Just to give you an idea of the sort of thing I'm planning on doing...

Guys, I am currently delving in deep researching front wall flush mounting methods and typologies, I will write a post on the main 4 different approaches I can think of soon, but, I have some questions to which I cannot find definitive answers regarding truly hard flush walls. Please note, I am not referring to the types of flush mounting techniques often used by forum members where baffle extensions are built in front of bass trapping, I am talking about the traditional Tom Hidley, Thomas Northward etc style massive flush walls. So, it is said a truly hard flush front wall must be solid, massively heavy and a continuous, air tight sealed baffle all the way to the side walls, floor and ceiling. It is in effect, the new wall of the room. It also becomes the new baffle to the monitors, the room and the drivers = the speakers. The walls are the cabinets, essentially. Now, what are the effects of introducing openings in the baffle, such as those often seen in Newell designs where the amps are racked in openings below/to the side of the speakers themselves? In other words, how do these openings compromise the huge massive baffle wall? Do the openings do away with the whole point of building a massive continuous baffle in the first place? My thoughts are that the baffle wall will act in a similar way to a speaker cabinet, if completely sealed it will be like an infinite baffle design where no low end can get behind the speakers themselves. If there are openings, then it will act like a ported speaker cabinet. If that's true, then in both cases of the completely sealed enclosure or ported, calculations need to be made to make sure the resonance in the cavity is low enough to not interfere with the direct sound, and if ported, that it is not colouring the direct sound. What are your thoughts on this? Paul

Hi guys, While waiting for your collective wisdom pertaining to my questions in my post above, I have a more pressing question. To update you on my roof situation; I have now ripped out all of the insulation from every rafter bay, and taken down all of the hangers. The ceiling is now naked. To make things even more heart breaking (temporarily) I have cut in two 1'x1' gable vents on each gable, so a total of 4 vents. I have also found a way to install soffit vents by installing them below the wall top plates; as there are large corner traps exactly where these soffit vents are located, for each vent I will need to make an air pathway through the insulation in the traps, up to the empty rafter bays above. Now I am considering whether or not to install a ridge vent as well. Here are the ventilation guidelines for the UK: https://www.wienerberger.co.uk/content/ ... nt_001.pdf According to those guidelines, I fit in to the very first example: my building is less than 10 meters wide, with a roof pitch of 22.5 degrees, and I have a non permeable membrane on the top of the roof deck (not an underlay, but still non permeable). That means I technically only need soffit vents and no ridge vent. However, if I were to put insulation on the ceiling which follows the rafter line (so behind my hangers) then I would assume I would fit into the example further down "Warm roof with impermeable (HR) underlay". Which means I would need a ridge vent, and the soffit vents would need to be increased to 25mm continuous air gap instead of only 10mm. So now I need to make the decision; do I install the insulation up there now so that it's done, and put in a ridge vent? then all I need to do in the future is block up all the vents and build my outer leaf, but in the mean time the internal room can be completely finished. Or do I go for option 1 and not install a ridge vent, then install the insulation up there in the future once the outer leaf is already constructed, and just live with the lack of treatment behind my hangers for now? If I was to install a ridge vent and put the insulation up in the ceiling then of course I would need to leave a 50mm gap behind the insulation, which is fine, but I am wondering if all these vents are going to make the place super cold and draughty in the winter... I am wondering if I should install a ceiling of homasote on the bottom of the rafters, which goes from ridge to eaves, leaving the necessary ventilation behind it, but keeping out some of the cold and draught. Then I can install the insulation on the face of the Homasote. So, after that long winded explanation, here is an actual question for you: If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption? Thanks for taking the time to read and I appreciate any answers you can give me, Paul

I guess everyone is clueless as me when it comes to my questions then :lol: I think I'll go with a soffit vents with an equivalent of a continuous 10mm free flow air path, keep the gable vents and install the rafter line insulation once the outer leaf is built, it's probably the cheapest and easiest option right now. I am still interested for the sake of future reference whether one would regard homasote (or other soft fibre board) as insulation or a mass when it comes to a MAM assembly. Perhaps it's both? Paul

Now, what are the effects of introducing openings in the baffle, such as those often seen in Newell designs where the amps are racked in openings below/to the side of the speakers themselves? In other words, how do these openings compromise the huge massive baffle wall? Do the openings do away with the whole point of building a massive continuous baffle in the first place?

Since the openings are very small, it shouldn't affect the infinite baffle concept. Only major changes in sheathing angles would mess it up.

My thoughts are that the baffle wall will act in a similar way to a speaker cabinet, if completely sealed it will be like an infinite baffle design where no low end can get behind the speakers themselves. If there are openings, then it will act like a ported speaker cabinet.

There is probably enough damping in the wall cavity to not worry about it acting like a ported cabinet. If the cavity wasn't fully filled then that would be a different story.

If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption?

Could you maybe just put up vapour barrier to tame the drafts? Your condensation shouldn't be an issue if there is good ventilation above the barrier, no?

Thanks for taking the time to read and I appreciate any answers you can give me

Sorry I haven't been around here too much lately. I've been busy as heck but you're the roof master these days anyway! Care to share some nightmare pics of your room with everything torn out? Keep your head up. It's going to be awesome when it's done! Greg

Gregwor wrote:

Now, what are the effects of introducing openings in the baffle, such as those often seen in Newell designs where the amps are racked in openings below/to the side of the speakers themselves? In other words, how do these openings compromise the huge massive baffle wall? Do the openings do away with the whole point of building a massive continuous baffle in the first place?

Since the openings are very small, it shouldn't affect the infinite baffle concept. Only major changes in sheathing angles would mess it up.

My thoughts are that the baffle wall will act in a similar way to a speaker cabinet, if completely sealed it will be like an infinite baffle design where no low end can get behind the speakers themselves. If there are openings, then it will act like a ported speaker cabinet.

There is probably enough damping in the wall cavity to not worry about it acting like a ported cabinet. If the cavity wasn't fully filled then that would be a different story.

If I did this, would the homasote act as a leaf? A rather light leaf, but a leaf none the less? Or would Homasote be considered absorption?

Could you maybe just put up vapour barrier to tame the drafts? Your condensation shouldn't be an issue if there is good ventilation above the barrier, no?

Thanks for taking the time to read and I appreciate any answers you can give me

Sorry I haven't been around here too much lately. I've been busy as heck but you're the roof master these days anyway! Care to share some nightmare pics of your room with everything torn out? Keep your head up. It's going to be awesome when it's done! Greg

Thanks for the reply Greg, I do have some nightmare pics haha I’ll upload them soon for your entertainment. I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers). Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity. What do you think? Paul

Paulus87 wrote:

I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers). Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity. What do you think?

It doesn't look like there's an easy to do this without having to take it down again Paul. If I were you I would staple it to the bottom of the rafters (not the rafter ties, so above the hangers) to avoid troublesome HF reflections whilst you're using the temporary room. How long are you planning on waiting before building the new outer leaf? Are you expecting another winter. If not I might not worry about the draught. But if you are it would probably be worth the trouble and expense to just put up some temporary vapour barrier above the hangers and then when you build the outer leaf, snip the cable ties on some of your hangers and then pull down the vapour barrier. You're kind of in uncharted territory with your inner as a temporary outer leaf, then build around it later studio build. Dan

Waka wrote:

Paulus87 wrote:

I thought about putting up a vapour barrier but where would it go? ... it’s supposed to go on the warm side of the insulation which means either under the rafter line insulation (behind the hangers) or in front of the drop ceiling at the rafter tie level (below the hangers). Either of those options would be fine except for the fact that I would have to remove it again when I build my outer leaf... as you shouldn’t have two vapour barriers in the same assembly and the vapour barrier would need to go on the warm side of the MAM cavity. What do you think?

It doesn't look like there's an easy to do this without having to take it down again Paul. If I were you I would staple it to the bottom of the rafters (not the rafter ties, so above the hangers) to avoid troublesome HF reflections whilst you're using the temporary room. How long are you planning on waiting before building the new outer leaf? Are you expecting another winter. If not I might not worry about the draught. But if you are it would probably be worth the trouble and expense to just put up some temporary vapour barrier above the hangers and then when you build the outer leaf, snip the cable ties on some of your hangers and then pull down the vapour barrier. You're kind of in uncharted territory with your inner as a temporary outer leaf, then build around it later studio build. Dan

Good ideas Dan, yes it is totally uncharted territory, I think I may even be the only person who has chosen to do it like this on the forum, I only know one other studio that was done like this which was a WSDG project. I thought of the hf reflection problem and was thinking I could combat that by just putting some more treatment below the vapour barrier... my thinking is, in a normal residential build the vapour barrier would be installed on the bottom of the rafter ties with the ventilated loft space above it, then the plasterboard ceiling in front of the barrier (facing the internal room below). I need to add removable ceiling panels there anyway, which will be wooden frames with stretch fabric and insulation. Then when it comes to removing the barrier I just take the panels down, pull the barrier off and then put the panels back up. Makes sense or no? Paul

Paulus87 wrote:

I need to add removable ceiling panels there anyway, which will be wooden frames with stretch fabric and insulation. Then when it comes to removing the barrier I just take the panels down, pull the barrier off and then put the panels back up.

That makes sense. I'm sure as a temporary measure it doesn't matter too much where you place it. Assuming you're not leaving it 5 years before you change it. Just go with wherever seems to be the easiest to remove it afterwards. Dan

Just to clarify I've drawn a diagram of the proposed plan. In reality, the soffit and gable vents would all act like inlet/outlet vents depending on the wind etc. The vapour barrier would be installed on the underside of the rafter ties then go down under my horizontal corner traps and then sealed to the walls. The soffit vents are actually installed under the wall top plates, and behind the horizontal corner traps; therefore I need to make sure there is an unobstructed path between the vents and the roof deck, I'll use some chicken wire or something just to keep the insulation out of the way. According to the roof ventilation guidelines in the UK a roof with an impermeable membrane (roofing felt) does not require a ridge vent or gable vents if: - there is the equivalent of a continuous 10mm air gap all the way along the eaves on both sides - the building is less than 10m wide - the roof pitch is less than 35 degrees - insulation does not follow the rafter line However, high level ventilation can be installed as an extra precautionary measure. I think due to the fact that the studio will not be subject to excessive moisture (such as in the case of a bathroom or kitchen), the combination of a vapour barrier, soffit vents and gable vents should be more than enough to keep the studio in good condition until I build the outer leaf. One pertinent thought I have though is if the vapour barrier is preventing the vapour from getting into my 'attic space' then where will that moisture go? It has to go somewhere. Therefore am I better off not installing a vapour barrier so that it can escape out of the vents? or am I better off letting it escape out of the wall ventilation system attached to the silencer boxes that will be installed? Thanks for all your help guys, it really helps me to keep going! Paul

What do you guys think of angling windows vertically instead of horizontally at first reflection points? For me, it could save a lot of floor space, since then I wouldn't need "soffit wings". The idea is to deflect the rays away from mixing area, and I am aiming for the entire width of the console (11'). The majority of rays would go up into the ceiling hangers/trap. My side walls would be about 1' thick with angled waveguide absorbers, so the angle of the windows can be sufficient to make this work, I think. What do you guys think? Paul

Paulus87 wrote:

What do you guys think of angling windows vertically instead of horizontally at first reflection points? For me, it could save a lot of floor space, since then I wouldn't need "soffit wings"

That's an interesting idea. It could work but only if you have the ceiling height and absorption. Will you get a 20ms+ travel time on the waves before they return? Also what about below the angled bits? Have you ray traced whether a ray heading off axis down and reflecting just below the angled bits and then off the floor and back up towards the mix position. Dan