when it comes to insulating an old house in a hot humid climate there's more to it than just stuffing the uninsulated cavities with insulation moisture is a massive concern both in the liquid form and the vapor form and if our old building assemblies can't dry out they support mold and rot this video is part two of a three-part series that I'm doing discussing how to properly insulate and retrofit older homes in the hot humid South if you haven't watched part one already I highly recommend that you go and watch it first as we covered how to address old slabon grade foundations pure and beam foundations and crawl spaces and some common wall assemblies I'll put a link to it up on the screen and in the description below today we're continuing with wall assemblies and then moving on to roof assemblies and the various considerations that you need to be thinking about as there's so much to cover when it comes to these areas without further Ado let's get started another type of reservoir cladding that we commonly see in the south is stucco stucco is extremely common and is often applied to wood framed walls typically separated by a couple layers of tar paper the first layer acts as a bond break and the second layer ser as the primary water control layer but sometimes we just see the stucco being applied directly to a single layer of the WRB or even directly to the sheathing we tend to see a lot of rot in these types of walls if there was an attempt to insulate those walls in the past if the walls are uninsulated we still see moisture issues though it's not as common as the insulated wall assemblies because those walls can actually dry out unimpeded but stucco in general can pose a lot of problems if it's installed on a woodf framed wall without an air gap to promote drainage and a capillary breake we have to uncouple the stco from the walls if we're planning to insulate we also see a lot of concrete block or CMU walls in the hot humid South and these CMU walls are either architecturally split-faced blocks that are left exposed as a design feature or they're painted or they're coated with some stucco and it can be quite challenging to retrofit insulation into these types of wall assemblies because CMU can absorb and store a lot of water and it doesn't distribute it evenly like a typical Mass wall as water tends to collect at the bottom of the ungrouted cells we've talked about retrofitting CMU wall in another video called insulating old cinder block walls the right way which you can go and watch right here I'll also put links in the description to these videos but we need to make sure that we're uncoupling these damp walls from the interior framed walls and the finishes if possible prior to insulating either with a dimple mat and a new interior perimeter drain or with a fluid applied negative side waterproofing combined with some other drainage practices to limit the amount of water being absorbed into those walls we can also use taped rigid foam insulation to uncouple those walls but we need to make sure that we're draining the bottom of the walls to prevent water from collecting and leaking inside to the interior now the best possible way to retrofit these types of walls is actually to provide a water and air control layer on the outside of the block wall usually a liquid applied or spray applied waterproofing and then a couple layers of rigid insulation and then some cladding that's fastened to that and then we basically have what we would call the perfect wall all of the insulation is on the outside like a styrofoam cooler we eliminate any thermal bridging we keep that block wall dry and we can keep those interior temperatures is nice and cool we talk a lot about this strategy and More in my guide to moisture management for residential remodels where we discuss how to control moisture and safely insulate a wide range of existing building conditions do it right the first time instead of having to come back a couple years later for a costly mold or rot remediation the guide is only available at aerd designs.com shop links will be in the description below now back to the video now this brings us to roof assemblies and how we need to address these existing conditions in CMU walls properly to avoid any embedded wood frame Fring from rotting away or any moisture accumulation in the sheathing and framing materials where roofs meet concrete block walls is one of the most complex conditions that we have to deal with as that CMU distributes moisture to the framing materials remember that concrete and masonry absorb and store a lot of water and they can distribute that water and moisture to other nearby materials like wood through capillary forces unfortunately we often see that the roof structure is either embedded into the concrete block often in the case of flat roof systems or it's bearing on top of the CMU wall without a capillary breake and when we go to insulate those walls those embedded ends stay wetter for longer because we're slowing down the heat flow and that's where we tend to see some problems occur and that's also why those older uninsulated buildings could get away with having no capillary breaks between the masonry and the wood so what do we do when we come across a condition like this and how do we terminate our dimple mat if we're insulating on the interior like the rest of the moisture sensitive components we need to uncouple the roof framing from the block walls which means that we need to cut those Rafters Away From the Block and provide a new place for those Rafters to bear on now we can either install a new interior bearing wall which may or may not make sense for your specific project it often involves retrofitting some new footings to make sure that the existing Foundation can actually support those loads at that specific location or we can bolt a steel angle to the interior of the block walls prior to cutting the rafters away and then when we do cut those Rafters away they're bearing on the steel angle that's fastened to the block wall rather than being embedded into the block wall itself now we do need to install some anti-rotational blocking to make sure that the existing Rafters don't twist and potentially turn over and we also might need to tie those Rapters back to the block wall with a restraining anchor but you'll need to coordinate all these things with your structural engineer now we're not done just yet we need to find a way to terminate that dimple mat at the top of the wall this is extremely tricky if we're dealing with a low sloped roof or a flat roof and it just so happens that we tend to see a lot of moisture related issues at this connection between the exposed CMU walls and the roof membranes usually in the form of blisters which are filled with water around the parapet transitions even worse we can see moisture on the interior dripping down from the roof structure at these locations and that often is mistaken for a leak so what exactly is going on here while we have all this moisture that's being stored in that exposed concrete block wall or masonry wall let's say we get a rainstorm and it pummels that block wall and the block wall absorbs all this water now when the sun comes out the heat of the Sun hits the surface of that wall and some of the moisture evaporates to the exterior but a lot of it is driven to the inside again that's why we have a dimple mat on the interior but what happens when it gets driven into that roof membrane that colls over the parapet we get condensation flat roof membranes are vapor impermeable whether you're using an EPDM or a modified bitamin or a TPO all of them are vapor impermeable and so when moisture and Vapor is driven to the back side of the parapet it has nowhere to go and the back side of that roof membrane is slightly cooler than the surface temperature of the masonry and we get condensation which results in moisture accumulation around that area it gets underneath the membrane at that parit transition and then we can see it drip down the backs side of the block wall we have to uncouple the roof membrane at the parapet from The Damp concrete block walls and so that means extending the dimple mat up onto the parapet and terminating the roof membrane through the dimple mat and then providing evented counter flashing to allow that moisture and Vapor to dry out and escape the roof membrane itself is part of the building envelope the rigid insulation installed below the roof membrane is also part of the building envelope and the framed walls below are part of the building envelope but the wet structure on the outside is completely uncoupled we do have one more step which is to address the parit cap or the coping we want to make sure that the coping is Ed as well because that block wall is going to draw a lot of moisture up like a straw especially through the grouted cells and we need that moisture to be able to dry out at the top we also get some drying through negative pressure induced by air flow at the top of the parapet if we bent that space and so the solution here is simply to install a highly Vapor permeable but water resistant membrane like Delta Fox over the concrete block and seal it to the top of the parapet wall and then we want to provide a vented space between the coping and that membrane either with some corrugated plastic or entangled mesh but we want to make sure sure that air can easily find a path inside and out the other end that's the end of part two we'll be back with a part three in the near future finishing up with Roof Systems so make sure to subscribe if you haven't already and stay tuned for that also make sure to give this video a like and in the comments below tell me exactly what you want to see in the future what types of problems that you're facing in your current remodels we've also got over 150 free building science articles many of which cover topics that we discussed in this video except at even greater depth for now good luck with your projects cheers [Music]