A Guide To Insulating Old Homes For HOT HUMID Climates (Part 1) | Floors, Foundations & Walls

when we go to insulate an older home in a hot humid climate we Face a completely different set of challenges than if we were to insulate a home in a cold or a temperate climate we have a lot of heat and moisture in the air trying to make its way inside which can cause condensation to form on the back side of the drywall or the finishes and that can support mold growth and rot within the wall cavities we also have to contend with the fact that when we go to insulate any incidental dehumidification benefits provided by the air conditioning system are essentially eliminated since we've reduced the loads on the air conditioning system as that cool conditioned air stays in the home for longer increasing relative humidity levels unless a dedicated dehumidifier is provided over ventilating with fresh air systems like ervs can also dump a whole bunch of moisture from the outside into the home and raise relative humidity if we aren't careful and so insulating existing buildings in these types of climates can be more complex than what meets the eye in this video we're going to walk through several common existing building conditions in the hot humid South and discuss insulation strategies that work as well as how to address common sources of moist and how to prevent future problems so that your old home can remain dry and durable for many more Generations we have a lot of stuff to cover so we're going to jump right into it starting with floors and Foundations most homes in the hot humid South are either built on slab on grade foundations pure and beam systems or crawl spaces we don't see a lot of basements in the South as temperatures are significantly warmer than the North which means that the footings don't have to be located nearly as deep to protect them from frost but also because many parts of the hot humid South have challenging or unstable soil condition I conditions and many parts of the South are marshy and have a high water table and are also in flood zones here we have a slab on grade Foundation this is a monolithic turn down slab which is probably the most common type of foundation that you'll see in the hot humid South and there's a lot of benefits to this type of foundation it's obviously an uninsulated slab if we're dealing with an older uninsulated home but having it coupled to the ground can actually provide some thermal benefits you have a very stable ground temperature which means that the slab is going to stay cooler concrete is a thermal Mass which means me that it can absorb and store heat and it has a very high specific heat capacity meaning that it takes a lot of energy to actually heat up that slab if the slab is in contact with the ground and so a lot of people like to have a slab on grade Foundation to passively cool their homes without running the air conditioning systems all the time now unfortunately older slab on grade foundations can leak they can Wick water if the adjacent soils are saturated and especially if a vapor barrier wasn't installed underneath the slab and that moisture ends up on the inside being distributed to the interior materials if there's no capillary break underneath the sill plates moisture can Wick up into those wood components and if we add insulation to the stug cavities it can rot out the sill at the outside of the slab Edge we can also get a lot of moisture that wicks in if the sight is poorly drained and if water collects around the footings and that water is drawn to the interior because concrete is highly porous and can Wick water very far distances and so you may notice damp spots or moldy or mildew odors or elevated humidity levels and those can be some obvious indicators that you have moisture wicking in from the slab especially if you're noticing these issues after a storm or a precipitation event so all this moisture has to be addressed prior to insulating to ensure that our moisture sensitive interior materials and components remain dry and durable first off we have to make sure that we have good sight drainage practices and that we're sloping the grade adequately away from the foundation to make sure that we don't have water collecting around the footings and being drawn inside and we want to make sure that we're directing that water to a dedicated storm water facility on site we want to make sure that we're not discharging our gutters and our down spouts anywhere near this Foundation again because we want to keep the edge of the slab dry and it also may be necessary to install a French drain or a new perimeter drain system that's set in crushed stone and wrapped in Filter Fabric like a new typical foundation and discharged to Daylight to make sure that any water that collects around the foundation is drained away from the house we also may want to coat that slab edge with a water repellent paint or apply a layer of waterproofing or damp proofing to break capillary continuity and to provide a water repellent surface now we also probably need to provide some form of vapor control in these older slabs and so this can either be provided by coating the slab in a fluid applied epoxy or some other vapor barrier coating or if we have especially wet conditions in the slab and you're noticing small puddles forming in the slab or dampness then it may be necessary to install a sealed dimple mat over the existing slab to not only provide a vapor barrier but to completely uncouple the interior from The Damp slab and to prevent any additional moisture from wicking in we've talked about this strategy in depth in another video called insulating and sealing existing slabs where we use a dimple mat to break capillary continuity and to equalize vapor pressure so we don't get any additional moisture wicking in and try to dry into this space and so that air gap provides a lot of benefits and a diml mat is what we use very frequently in retrofits as a potential solution to a wide range of problems that involve capillary wicking moisture and drainage now it's still beneficial to insulate these slab on grade floors to keep the interior temperatures nice and stable it's not 100% necessary but it can be beneficial especially if there are some months where temperatures are generally colder I'm sure we all remember the bizarre freeze and Texas in 2021 and so installing a 1in layer of rigid insulation is more than enough to provide a thermal break and keep those interior temperatures consistent remember insulation not only helps to keep homes warmer but also help to keep homes cooler insulation slows the flow of heat so I promise your home won't overheat by insulating your slab now we can simply install this rigid insulation over the taped dimple mat or over the slab if your slab is relatively dry tape the joints of the rigid insulation and then install a couple layers of subflooring with staggered and offset joints to provide a substrate for the final floor finishes now if you want the appearance of a concrete slab you can install a thin 2-in topping slab over that rigid insulation and then you get the benefits of a thermal Mass that's uncoupled from that damp old wet slab and so that topping slab stays cooler for longer if you're air conditioning the space and it will also stay warm if you're heating the space so there's a lot of benefits to having this topping slab over rigid insulation to keep those temperatures nice and stable so that you're not having these large swings in temperature now in this section the slab on grade Foundation is used in combination with a 2x4 wood framed wall and wood cladding but we also commonly see this condition with a brick veneer in hot humid climates so let's take a quick look at that in this section you can see that we have a brick veneer that's been installed and at the base of the wall you can see that there's a ledge that has been integrated into the slab's footings to support that brick veneer now the strategy that we would use to insulate the slab in this condition doesn't really change too much with the addition of the brick veneer however we do have to mitigate the amount of moisture being driven inside and both the liquid and vapor form brick is a reservoir cladding which means that it absorbs and stores water and so we have to be very careful about how we insulate this wall especially if there wasn't a weather resistive barrier on the sheathing behind the brick veneer we need to make sure that we're slowing down that Vapor that's being driven inwards otherwise we could have condensation form on the back side of the drywall if we're air conditioning that space and that could support mold growth if that moisture can't dry out and if we're adding insulation to that wall it's going to have an even harder time drying out this gets even more complicated if we don't have ventilation inlets and weeps at the bottom of the wall and ventilation outlets at the top often times in these older walls with brick veneers you'll see that the air gap between the veneer and the sheathing or the WRB is clogged with mortar droppings which reduces the effectiveness of the ventilation space and reduces the drawing potential of these walls so this is a major consideration that we need to be thinking about when we're insulating homes in hot humid climates now moving on you can see in this section that we have an older house bearing on a pure and beam foundation and a pure and beam Foundation is essentially just a crawl space without the exterior stem walls and so we get a lot of air flow on the underside of that floor framing which helps to prevent moisture from accumulating whereas a traditional crawl space can get quite humid and stuffy another benefit of these pure and beam Foundations at least in uninsulated homes is that all this air flow helped to keep the floors cooler by flushing out any stagnant hot air now I'm not so sure about that but people swear by it now this actually changes when we go to insulate these types of floors especially if we have air conditioning installed in the space this is because when we go to insulate at the floor level the interior conditioned space stays colder and if we have the AC running the temperature of the subfloor and finishes is cooler the temperature out here is warm and the air is humid and that's going to want to come inside and when that warm humid air comes into contact with a cool surface it has a high likelihood of condensing which can end up quickly rotting out the joists and the framing at this location so it's really critical that we not only have an air barrier installed in the floor assembly to uncouple the exterior environment from the condition space but we also need to have a vapor retarder installed in the right location to prevent all that inwardly dri vapor from condensing on the underside of the subfloor we don't want to install any vinyl flooring in these types of systems because that vinyl flooring is vapor impermeable and if moisture got inside it wouldn't be able to dry out and it would rot the framing out even quicker and so we want the air barrier and the vapor impermeable layer to be located on the underside of the floor joists now this Vapor retarder can either be in the form of a self-adhered or fluid applied Vapor impermeable membrane or we can use taped rigid foam insulation rigid foam is a vapor retarder and taping the joints can provide the benefits of an air barrier so we can use either of these solutions to air seal and prevent condensation on the underside of our subfloors in a hot humid climate we can also use these strategies for a standard vented crawl space as well although it's a lot more labor intensive especially if you don't have enough clearance between the grade below and the bottom of the joists now in a pinch you can use closed cell spray foam to provide the benefits of an air barrier and a vapor retarder however we're finding out a lot of nasty things about spray foam and I'm not currently recommending it as a solution until we figure this stuff out but for now taped rigid insulation is a great option or an impermeable self-adhered or fluid applied membrane applied to a substrate like plywood that's installed on the underside of the joists we also have to make sure that any interruptions discontinuities or penetrations in that air barrier are sealed so every intersection between each beam has to be continuously air sealed either with an expanding foam sealant or a tape or any other strategy that can ensure a long-term air seal as air can transport moisture through air leaks in significantly higher concentrations than simple diffusion we're free to insulate the joist cavities with any vapor permeable insulation of our choosing whether it's mineral wool wood fiber fiberglass or cellulose but mineral wool tends to be preferred for retrofits as it's highly Vapor permeable it's non-combustible doesn't deteriorate if it gets wet and it will help promote drying when used correctly in a building assembly back to our woodf framed walls with wood cladding or sighing one of the most challenging things that we have to deal with is that the siding was very rarely installed on a rain screen system meaning that there is no drainage gap between the cladding and the WRB or sheathing and that meant that any water that leaked into the wall assembly or was driven in would be held in tension against the WRB now in an uninsulated wall this isn't a big deal because that water dries out relatively quickly and that sheathing can dry out and we don't have any problems however when we go to insulate that wall that wall has a reduced dry potential because there's less heat flow moving through that wall assembly therefore the wood framing stays wetter for longer and that can support mold and rot I already mentioned that we can also get condensation on the back side of the drywall in these climates that can also support mold but essentially we need to prevent any water or air leakage from getting inside our wall assemblies if we're insulating because we aren't sure how it will shift the moisture balance in the assembly so generally this means that we need to remove the existing sighting especially if it's in bad condition and install some new siding or cladding over a rain screen either in the form of entangled plastic mesh which creates a drainage and ventilation Gap we can use vertical wood furring to create a drainage Gap and a ventilation Gap we can use plastic ventilated furring strips as well if we're building in a marine climate or we can use a drainable weather resistive barrier product such as hydrogap SA or typ hard drainable peeling stick there are several other products on the market but we need to make sure that we have a drainage gap between our cladding and our weather resistant barrier in our wall to make sure that any water that leaks behind the cladding won't be held in tension it'll just drain harmlessly down the wall and it's drained out and away from the house if there's one thing that you can invest in for long-term durability it's a rain screen for the weather resistive barrier product I'm recommending a self adherer or a fluid applied membrane as this will bond to the sheathing and provide a monolithic water and air control layer so we won't get any hot humid air leaking inside that could find a cold surface to condense on it'll also provide a very robust barrier against water so if there's any leaks in the system they'll be localized Water and Air won't travel behind the WRB like a typical building wrap like tyvec as we tend to see a lot of issues both with water and air leakage in those types of products if the existing sheathing is in good condition you can keep it right on the building but if it's in bad condition and you need to replace it you may want to consider something more like Zip system as this is an all-in-one product where we have a fluid applied coating that's been bonded to a sheet of OSB and then the joints are taped to provide water and air tightness but we have a lot of options at our disposal here we don't want the weather resistive barrier to be too Vapor permeable as this can allow too much moisture to pass through the wall assembly at once so shoot for a product that has a vapor permeance around 10 perms and no more than 20 perms you can also get away with a vapor impermeable weather resistive barrier in this climate as Vapor Drive is predominantly from the outside inwards then we're free to insulate the wall assembly with any unfaced bat or blown in insulation of our choosing whether we're using mineral wool wood fiber cellulose or fiberglass or sheep's wool it really doesn't matter now we could also install some rigid insulation outboard to provide a thermal break between the hot temperatures outside and the interior condition space however we don't need it to prevent condensation in this climate because we actually don't get condensation on the back side of the sheathing and hot climates we get it on the interior side on the back side of the the drywall because Vapor Drive is from the outside inwards not from the inside outwards in a cooling dominated climate now as I mentioned before it may be beneficial to install a vapor impermeable weather resistive barrier product to prevent vapor from diffusing to the interior and raising interior relative humidity levels however we can also use rigid foam insulation installed outboard instead to slow Vapor flow to the interior and to prevent condensation on the back side of the drywall as rigid foam as a vapor retarder so we have several options at our disposal but we do not want to install any kind of vapor barriers or vapor retarders on the interior side of the walls as this will likely result in condensation and mold pretty quickly as moisture won't be able to dry out to the interior now as I mentioned before we have several types of wall assemblies that are quite common in the hot humid South just beyond the standard wood framed wall with sighting we briefly touched on walls with brick veneers but now we're going to discuss how to address these assemblies more in depth here in this section you can see that we have a 2x4 framed wall with a brick veneer cladding we have a 1 to 2in air gap between the sheathing in the brick veneer we usually see a layer of tar paper or felt separating the sheathing from the veneer although there are cases where the waterproofing or the weather barrier has been omitted between the veneer and the sheathing which can significantly complicate whether or not we can insulate that wall assembly and then we have our 2x4 framed wall and so we really need to make sure that we're analyzing the moisture content of these materials prior to insulating especially since we have a reservoir cladding installed adjacent to moisture sensitive framing now as I mentioned before this is going to be trickier to insulate because we have to deal with all that moist moisture and that moisture Reservoir in the form of the brick veneer because that brick absorbs and stores a lot of water and wants to distribute it inwards because moisture moves from warm to cold and from higher concentrations to lower concentrations and so if we have a brick veneer that's holding on to a lot of water we're going to have a lot of vapor drive inwards so the first step in addressing a condition like this is to reduce the absorption of the Brick by enhancing the water repellency of the veneer for example by applying a siline or a saloane penetrating sealer to the brick veneer to create a hydrophobic surface while allowing the walls to dry out to the exterior silanes and siloxanes are highly Vapor permeable to promote drying but they significantly enhance water repellency so water beads off the brick rather than being absorbed by it however it doesn't bridge over cracks and gaps so water can still Wick through those openings but overall it will reduce the amount of water being absorbed by the brick and distributed inwards so this is a good first step no matter what now whether or not you have a weather resistive barrier like tar paper building wrap or building felt on these walls as a water control air will ultimately determine if you can insulate this assembly if you have tar paper or a weather resistant barrier that controls bulk water entry from water that leaks in through the brick you're probably okay to insulate these walls granted that you don't see any evidence of water staining or an elevated moisture content in the sheathing or the framing materials it's really critical that you take these moisture readings before ever insulating to address any potential issues and to determine whether insulating is even an appropriate option if you don't have this water control layer I would advise against insulating this assembly because you're going to have moisture constantly drying through the wall assembly and potentially leaking in through the air gap between the brick veneer and the sheathing if it's clogged with Mor droppings at some locations so you could have Water Bridge through and leak into the sheathing and that water needs to be able to dry out if you go to insulate these walls this will reduce the dry potential and those walls will stay wetter for longer and you'll likely see mold issues or rot in the future that could turn into a structural problem relatively quickly so it's crucial that you inspect the sheathing and the framing for any signs of water damage water staining or mold if you see any of that do not insulate if you know for a fact that you have a water control layer on the outside of the sheathing and you're not observing a higher moisture content then you should be able to insulate with mineral wool which is moisture resistant it's vapor open it's not food for mold and it will help to facilitate drying I would not use any kind of blown in cellulose fiberglass or wood fiber as these could pose a potential risk fiberglass deforms if it gets wet and cellulose can deteriorate if it gets wet even with the borate treatments we want to avoid spray foam altogether here as well as closed cell spray foam will inhibit inward drying open cell foam might allow for drying but we still see issues with it behind Reservoir claddings we also want to avoid any bat insulation with plastic or foil facers as these are vapor barriers so it's really important to take the insulation specifications into consideration then we want to specify a moisture resistant interior finish material such as a fiberglass matte face gypsum product like Den's armor and this essentially is a drywall product without the paper facers paper facers will support mold growth because it's an easy to access food source for the mold if moisture is present but fiberglass mats are inorganic and won't support mold growth because mold can't consume it so this would be the safest option and we want to make sure that we're using a vapor open paint so moisture can dry out to the interior unrestricted do not use any epoxy or oil-based paint it may also be necessary to install an additional Vapor permeable air barrier membrane on the interior side of the studs with a surfice cavity to avoid using the drywall as an air barrier as we tend to poke a lot of holes through our drywall and those holes aren't generally well air sealed we use this strategy in cold climates but it can also be used in hot climates as well as long as the air barrier membrane is vapor open guys that's the end of part one make sure to subscribe to catch part two next week and turn on notifications so you don't miss a single video If you're looking for a complete guide on how to remodel your old home properly get my moisture management guides residential remodels where we discuss how to control moisture and safely insulate a wide range of existing building conditions that's only available at A-D designs.com sshop links will be in the descript description below 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 make sure to give this video a like if you haven't already and subscribe for more weekly building science content for now good luck with your projects cheers [Music]

Channel: ASIRI Designs

Views: 4,151

Keywords: Insulating old homes, insulating, old, home, old house, old building, insulate, how to insulate, in hot climate, hot climate, hot, humid, climate, hot humid climate, warm, moisture, humidity, humid climate, retrofit, remodeling an old house, texas, florida, georgia, lousiana, vapor, dehumidifier, insulation, building science, asiri designs, how to, details, hot climate details, construction details, warm climate details, walls, existing, how to insulate an existing slab, pier and beam, crawlspace

Id: 1TuRK3CI7jc

Length: 19min 24sec (1164 seconds)

Published: Sat May 04 2024