Can someone 'in the know' read this article?

Hi I'd like to know if I can get someone really good here (or anyone at all) to chime in about some things written in the article linked below.... Particularly, I'm kinda thinking some of the treatments of a basement are not quite inline with what we are told how a studio should be constructed (e.g., they say no vapor barriers on any basement wall constructions, and that insulation in the basement ceiling is a 'bad idea') I was a bit confused by some stuff... Hoping people could clarify/explain/support/defy.. thanx, K http://www.buildingscience.com/resource ... novate.pdf

Luftweg, I have come across this publication in the past – and do not readily agree with all of their positions regarding these issues. First off – I never let anybody think that they can just let humidity levels run wild in their spaces – I point out that it’s critical they maintain humidity levels (relative of course) of 40 to 45% maximum in order to assure that problems relating to mold and mildew will not surface. If this can be handled through the use of normal heating / air conditioning then fine - if not then they need to add dehumidifiers. In addition I would point out that all of the details (in this publication) indicate them considering wall assemblies that are tight to the inside face of the foundation – which (and they are correct on this point) will not breathe – HOWEVER – we always recommend a minimum of 1” clear air space between wall assemblies – thus our construction WILL breathe freely. I would also point out that they are picturing this backwards (in a basement anyway) as regards condensation. With the exception of the most extreme climates – ground temperature is generally around 54 degrees once a depth of roughly 48” is reached. Meanwhile – inside of the room we construct the temperature will generally be maintained (even in air conditioned rooms) between 68 and 70 degrees F. Thus it is the warm moist air in the room that will reach dew point upon reaching the inner surface of the foundation wall. This is NOT where we want this moisture to go. We typically place vapor barrier within the outside walls (in walls exposed directly to outside exposure it’s the inner face in cooler climates and the outface in warmer climates) while we do not place those barriers on the ceiling. Attics are typically dryer (relative humidity wise) than the inside of the building – and (if properly vented through the use of soffit vents with ridge vents (1st best choice) attic fans (2nd choice only because of energy costs) or gable vents (last choice because they are typically wind dependent to work really well) they will have a lower pressure level than the remainder of the home. This means that the humidity within the space will naturally migrate towards the attic, or (in the case of a cathedral ceiling) to the cavity at the top of the ceiling joist that should contain a proper vent to allow the free flow of air. As the floors above loose their humidity in this manner (along with through any exhaust that might exist such as dryer vents – bathroom fans – ducted kitchen exhaust fans and fuel fired hot water heater or boiler flues) the humidity in the floors below (including the basement) migrate upwards. Insulation within the ceiling of the basement (without a vapor barrier in that location) does not affect this natural migration from taking place. I have never had an issue in this regards – in fact – in homes (in the US) that utilize electric heat – it is a code requirement that basement and crawl space ceilings be insulated. So of hard to escape from that when constructing a new building or addition. This leaves the issues they raise regarding ground water migrating into the building either through the wall itself or through the floor. We are always careful to explain to people that if this condition exists they have to deal with it in some manner before constructing their basement studio. One manner that I recommend is through the use of an interior perimeter drain, a simple slot along the wall / slab joint will suffice if the water is coming in small amounts through the wall. This can then be run to a sump pump or to footing drains if they exist.. If the water is coming through the slab itself due to high water table – then things get a bit trickier – I’ve been in situations where I have had to remove the entire basement slab – install 2’ of crushed rock – with a crisscrossing series of 4” drain pipes at the base of the stone – with this then running to a pair of sump pumps that had controls installed so that they alternated operation ( this to increase the life of the pumps) as well as operated in concert if one couldn’t maintain water levels during the heaviest of rains. The point here is that one way or another everything begins with infiltration of water being dealt with prior to basement construction taking place. In a dry basement I have no issue with the installation of flooring directly over the concrete slab. In over 30 years of construction this has not caused issues in basements properly prepared for the installation. I hope this clears up your questions – although if you have more I am only as far away as your keyboard. Sincerely, Rod

Thanx Rod.... needed your analysis.... I do have further questions, some about the article, some about things you just wrote.. I will formulate them shortly.... K

Rod, when you wrote this...

In addition I would point out that all of the details (in this publication) indicate them considering wall assemblies that are tight to the inside face of the foundation – which (and they are correct on this point) will not breathe – HOWEVER – we always recommend a minimum of 1” clear air space between wall assemblies – thus our construction WILL breathe freely

. Were you saying there should be a 1" clear air space (no insulation) between the foundation (slab wall in my case) and the frame (with insulation) as in the picture below? (In the pic I only allowed a 1/2" air space between my slab wall and my frame. I had also planned for my insulation to touch the slab wall...Is this incorrect?) I'm assuming you're not speaking about inner walls (double walls) as I have seen it stated here that the insulation between walls should "touch" and be lightly compressed. I wouldn't assume this is "clear" air space (although we refer to it as "air space"), but these are not "foundation" walls either if I'm understanding what you're saying

camistan wrote:

Were you saying there should be a 1" clear air space (no insulation) between the foundation (slab wall in my case) and the frame (with insulation) as in the picture below? (In the pic I only allowed a 1/2" air space between my slab wall and my frame.

Cam, I like to see 1" of clear space between walls - specially at the foundation - it really allows things to breathe freely -

I had also planned for my insulation to touch the slab wall...Is this incorrect?)

Not only is that incorrect - it's actually bad - the insulation should never touch the slab - if it does - then cappilary action (like a sponge) can suck moisture from the face of slab to the insulation - and insulation looses it's value when it's wet.

I'm assuming you're not speaking about inner walls (double walls) as I have seen it stated here that the insulation between walls should "touch" and be lightly compressed.

Well you've never seen that stated by me. I advocate that people use nylon strapping - applied to the back of their wall assemblies - to make certain that the insulation can't sag over time - this would automatically assure that there is an open (free air) space between the layers of insulation. Rod

Hi Rod, assuming existing block walls, should there be a vapor barrier between the insulation and the block wall or no vapor barriers (internally) at all? (btw - have your book - a must read for all people serious in learning about the proper techniques for building a studio...)

Rod: (as I notice you are now getting inundated with questions in this thread -- sorry about that) In regards to the perimeter drain.... What is your position on surface level drains, or perhaps drains of minimal depth? My plan was to resurface the concrete floor by grinding it rough, then apply an MRB (moisture reduction barrier), and then a surface (with some precentage of epoxy solids). THEN, leaving about a 2 to 3 inch gap between the PT (inner leaf) baseplates and poured concrete wall, I would run an L-shaped vinyl (or maybe pvc barrier) 'gutter' -- between the baseplate and the concrete wall, leaving a gap for water from the wall/floor joint to flow into (this would be affixed with polyurethane or epoxy adhesive). These would run behind the entire perimeter of the basement and lead to either one of the sumps... Now, should there be any sort of 'bleed' areas left at the junction of the concrete wall and floor (i.e., should I omit the MRB and resurfacing along that 3" gap behind the baseplates? -- this would keep the level along the wall 1/4 to 1/2 lower, and keep that area a touch more permeable than the middle of the floor)? Should weep holes be deliberately made at bottom of wall (I don't think so)? And should there be a venting of the space between the concrete wall and the inner leaf? (if not, how does one 'seal' up the air space, and yet allow the perimeter drain to lead to the sumps?) (note: I would also be resurfacing the walls, but not with an MRB, but rather simply something like thoroughseal) Next: Is it okay or advisable to use PT for the entire framing... -- in the event of this 'inevitable' hurricaine we are supposed to be getting in New England... (i.e, in an emergency, if water DOES end up going over the height of the baseplates, or if water wicks through the baseplates, the studs would get wet). And -- although I know your position on cement board being not necessarily 'tried and true' , and that an equivalent mass might decrease the layers (since it's much denser) and reduce sealant redundancy (because less layers would be needed) -- would cement board be good with respect to the whole moisture damage prevention scheme? (I was just reading of how a university's physical plant installed cement board on the WALLS of basements in school hall renovation (they used green board on the ceilings); this was done with moisture in mind). thanx, K

Cam - "I'm assuming you're not speaking about inner walls (double walls) as I have seen it stated here that the insulation between walls should "touch" and be lightly compressed." Rod - "Well you've never seen that stated by me. I advocate that people use nylon strapping - applied to the back of their wall assemblies - to make certain that the insulation can't sag over time - this would automatically assure that there is an open (free air) space between the layers of insulation." OK, Rod - assuming both sides of the above wall are in identically conditioned space (as in, same studio) I'd think that there would be literally no vapor movement thru the wall ANYWAY; so in THIS particular case is it really important to have an air gap (as opposed to complete fill of fluffy fiberglass) ? (Not being argumentative here, we're getting enough of that in the Acoustics forum these days :? ) Enquiring minds, an' all that :wink: Steve

knightfly wrote:

.... assuming both sides of the above wall are in identically conditioned space (as in, same studio) I'd think that there would be literally no vapor movement thru the wall ANYWAY; so in THIS particular case is it really important to have an air gap (as opposed to complete fill of fluffy fiberglass) ?....

That is a really good question Steve; I can't wait to hear the responses... But I was wondering if there would not be vapor potentially condensing on the cold concrete floor (between baseplates), or seepage coming through the concrete that would need to dissipate? If there is a vapor shield behind the inner-leaf mass along the exterior side walls, should there be vapor shields behind the interior wall leaves, IF the dead air space is contiguous between all double walls (or else, how would one stop vapor from going through an interior wall and travelling along the shared dead air space and condensing on the concrete?)? BUT, how would this be done?: If it's put only on one side of an interior wall, then the vapor could just as well go through the other side, no? If it's put on both sides, then there is the risk of actually locking the vapor between the leaves, no? (I should probably draw a diagram to illustrate my question... ) It almost seems better to not put any vapor barriers in at all; if not put in to block all the paths, then it would be a waste of time; if put in to block all paths, locking-in of moisture seems a distinct possibility... (So, why not just vent the dead air space (through baffles and/or along perimeter drain) and omit the vapor barrier?). Alternatively, could having an air space in internal doubled walls be an advantage to allowing contiunous 'venting' from the concrete walls, IF they share the same dead air space (and if not, how does one separate those spaces and yet prevent flanking?)? Also, what exactly is the sound transmission blocking advantage/disadvantage of filling the space completely versus allowing a small space between insulations of the inner and outer leaves? In the event that water DOES get between the leaves, allowing it to vent quickly sideways and upwards appears to be a 'good' thing, no? thanx, K

Here is a (crude) drawing showing some possibilities of moisture travel through walls and ultimately on the concrete wall (or the reverse?)... Note that, if the dead air space between the inner and outer leaves is contiguous from exterior to interior walls, moisture looks like it could go through an interior wall (with presumably no vapor barrier) and travel the dead air space to the concrete wall behind the exterior inner leaves (which presumably do have vapor barriers). K

gullfo wrote:

Hi Rod, assuming existing block walls, should there be a vapor barrier between the insulation and the block wall or no vapor barriers (internally) at all? (btw - have your book - a must read for all people serious in learning about the proper techniques for building a studio...)

Again, I'm not 'in the know', but I don't think you'd want any vapor barriers behind the insulation... The insulation is there to keep the interior wall surface 'warm' I think... then the barrier is in front of the insulation (interior to it) so that no vapor will pass through (and the vapor won't readily condense on the interior wall surface, because it's too warm there, and better vented). If you put the vapor barrier on the concrete, and no vapor barrier interior to the insulation, then vapor will pass through the wall to the vapor barrier, BUT the vapor barrier will be cold, so vapor could condense on the barrier and collect between the inner and outer leaves (and of course, it can't go through the concrete to the outside world). And if a barrier is put both on the concrete AND behind the insulation, a vapor 'lock' could be created, no? ... (I think everyone knows this one is bad; would it be infinitely better to not have any vapor barrier than this?)... The only way I could see that putting the vapor barrier behind the insulation would work, is if the concrete were much warmer than the interior air -- and I don't believe that ever happens in a basement, or does it? Certainly not a burried basement up here in New England... I don't believe that it makes much a difference whether the wall is block or poured concrete.... if that was your question.... HEY, someone in the know please confirm or deny this before I get myself in trouble! lol :lol: thanx, K

knightfly wrote:

OK, Rod - assuming both sides of the above wall are in identically conditioned space (as in, same studio) I'd think that there would be literally no vapor movement thru the wall ANYWAY; so in THIS particular case is it really important to have an air gap (as opposed to complete fill of fluffy fiberglass) ?

Steve, Actually we're talking to totally different issues here, the first being vapor as it relates to condensing on a concrete (or block for that matter) foundation wall - and the issue of the value of an entire cavity being filled with insulation. Let's deal with the first issue first. We know that granted a large enough variance in both temperature and humidity that a cooler surface will create dew-point conditions - which is why (in a perfect world) we want a vapor barrier (another place I disagree with that paper - I do not want any warm vapor entering a cavity where it can then condense) and we want it placed on the warm side of the wall. So the inside of the wall in the north - and the outside in the south. The foundation wall poses an additional problem in that it's always possible for some weeping to occur - and we do not want our insulation to get wet - so we maintain distance from the wall with our insulation - and the easiest way to do this is through the use of strapping. Now on to the 2nd situation. Although you are correct that given one common HVAC system - multiple rooms will maintain the same humidity levels - this is not true with multiple systems. As I explain in the book (in some great depth I believe) there are drastically different latent loads when you compare a live room (tracking) to a control room. You have very low latent levels in the control room - but very high levels in a live room when a band is rocking it's socks off. That's why it's so difficult to design a common system for rmultiple rooms. In this case migration can affect the operating efficiency of the various systems - for example - raising the humidity levels in a control room to the point where the system (which is designed for primarily greater sensible loads) can't maintain the desired humidity levels. So in general - in commercial facilities - I want to maintain distinct envelopes within each space controlled by each HVAC system. This has nothing to do with concern regarding condensation - but strictly HVAC effeciency. As far as a basement studio goes- I wouldn't consider this to be one of my largest concerns....... most people are lucky to have one decent systems installed - at which point the distributed air would maintain consistent levels in all rooms - and our primary concern then becomes stopping the potential for condensation on the foundation wall. I am very big on suggesting the use of dehumidifiers to aid in this manner - but proper control of vapor is also important. As far as the suggestion regarding insulation not touching (i.e.: the use of strapping to hold the insulation within the cavity so it doesn't sag) although I have seen clear evidence that insulation within a bay gives isolating value to the assembly (apparently due to it's ability to damp the face of the wall) I have not seen any exidence that filling the cavity completely with insulation (versus the 1" air space) gives any added benifit. All I see is added cost. SO, since I am not convinced that the additional 1" of insulation has any value whatsoever in isolating room to room, I do a cost analysis - 2 2x4 walls with R13 insulation within the cavities versus 1 wall with R13 and one wall with R19 - and I find that i cannot justify the added expense. It's just the way I see it. Sincerely, Rod

Gotcha, and I agree completely; my reasons for recommending slightly compressed fill for interior walls were mainly for ease of construction; it can be difficult for some people/situations to put strapping on the inside of two adjacent wall frames, as this normally would require that the frames be strapped while laying on the floor and then tipped into place (depending on your method of attachment of the strapping) - given your added reasoning on HVAC concerns though, my concept of inner walls and vapor obviously needs to be adjusted :roll: Thanks for clarifying that; I've still not found enough time to finish ALL your book - damn sleep anyway, I still think it's over-rated... Steve

Rod and Steve: So do this mean that the vapor barrier should block off the dead air spaces that extend between INTERNAL double-leaved walls? I'm a bit confused... thanx, K