I’m recommending we NOT INSULATE This Old House

[Music] on the build show today we're going to answer the question do i insulate my old house now here's the situation 100 year old house not quite 1920s house under renovation here at fort worth my buddy brent hull is doing this renovation project and here's a wall that's opened up and when i first walked into the house i was shocked to see on this house that's almost 100 years old that the sheathing on the outside of the house is some kind of old-school particle board look at this this is this is like ikea furniture minus this is garbage i'm not even sure exactly why they used it and it does not look like there's any tar paper or anything asphaltic on the outside so you would expect on a house that's brick and not much overhang that this would be falling apart or maybe would be molded or rotted but in fact this is an amazing shape this hundred year old particle board is still in excellent condition i pulled this out from another section of the house so then i say to myself if we're going to insulate this house and bring it up to modern standards how do we do that without causing a problem without doing something different now this wall cavity had never had any insulation in it but what's interesting is this wall cavity over here in this little section have had some renovation over time so this cavity 1928 let's say this cavity about 15 20 years ago got renovated and the window got smaller this is the original sill and when they renovated they put this stuff in there's some pink insulation in there and then they re-plastered in that area to match and they also put some tar paper on the inside now one bay over over here this was probably done in the 1940s and this has some original kind of rock wool insulation some mineral wool based insulation and if we take these bats out it looks to me like they re-sheathed this area with some solid sheathing now what's interesting about this is that again there's no rot there's no mold why is that in a modern building with no overhangs and brick and some particle board sheathing we would see some serious problems especially because there's lots of holes in that sheathing there's lots of airflow and remember brick on the outside of a house absorbs water every time it rains so every time it rains on the outside of this house that brick is absorbing gallons and gallons of water and then when the rainstorm stops and the sun comes out the sun is beating on the brick and it's drying it to the outside but it's also driving a lot of that moisture to the inside they call that vapor drive so a lot of that moisture is wanting to come into the house got a couple things going on here though solid sheathing solid old growth studs and real plaster on the inside of the house and what is plaster plaster's masonry right it's mortar basically so all these materials are highly absorbative and because they're solid products they're not going to rot they're not going to mold they're not going to break down they're going to absorb that water and they're going to release it over time so let's go back to our original question that we posed in the video should we insulate these cavities it's a tricky question where this sheathing is here i'm really hesitant to insulate these cavities and change it especially if i'm going to put sheetrock on the inside which is a modern building material that has paper facing on the back side there's holes in this we could get air flow through here we're certainly going to get moisture and vapor through here if we add insulation and then sheetrock we could have some problems your client might come in this house in two or three years and go it smells musty in here what's that musty smell we could have some mold growing on the back of that paper facing on our sheetrock we could this particle board would certainly start to break down if it wasn't able to dry easily and i mentioned that these solid studs in this solid sheathing were less prone to that and the plaster was less prone to that let's talk just for a brief second about why rotten mold happens rot and mold tint or mold in particular tends to happen on cellulose that's a fiber that's a wood product that's food for mold and it tends to happen on wood that's more broken down so for instance you would rarely see mold growth on the side of a two by four and you sometimes see it though on the back of sheetrock or other things that are more broken down that's paper so this wood fiber is more broken down than this two by four i might expect to see if there is some water in this cavity some mold growing potentially on the back of this broken down wood product and i didn't see this when we were first talking but if you look into this cavity down here where the bottom seal is where the house sits on the foundation and the brick stops there is a little bit of brown staining that who knows if it's mold or not it's really it doesn't really matter the point is it's not rotted it's not soft or punky but there may be something happening there and it's not happening at all on the wood on the plaster on this solid sheathing that's on this portion of the house over here so we need to be really cautious when we do renovations on old houses now this is a pretty historic house pretty gorgeous old house we're in a historic district i'm going to recommend that brent talks to the historic commission talks to the building inspector and say you know i'm not sure that we should insulate these areas we're better off spending a little bit more money in energy heating and cooling this building then we are adding some insulation and saving a hundred dollars in heating and cooling costs but causing this sheathing to rot or mold on us now on the other hand in this cavity right here with the solid sheathing this solid you know old-school shiplap sheathing this had rockwool type insulation that was added around the 1940s in fact you can kind of see the patent date in 1939 in this insulation that's pretty cool this is in perfect condition if we're going to insulate this i'd go back with a simra type of insulation i would use a new rockwool insulation bat in this cavity and again i might be cautious on a house like this adding sheetrock on the inside anytime you can go back with plaster in a house that had plaster you're going to be better off this plaster doesn't have any paper facing there's nothing that could cause rot or mold or problems in the future so in the end it's a tricky question be cautious about insulating a 100 year old historic house like this you don't want to change the conditions that the wall's been under that made it last and survive and not have a single bit of problems on the other hand if you open a house like this up and there's a bunch of rotten mold you got to figure out where the problem is usually it's airflow or water flow that's coming through the cavity and that's what's depositing that moisture if it can't dry it's going to die my buddy david decastro says this wall cavity was able to dry over all those last century of years 100 years and because it could dry it's in perfect shape today guys if you're not currently a subscriber hit that subscribe button below we talk about building science we talk about product reviews we've got all kinds of nerdy discussions here with the whole intent of building a more healthy more durable more efficient house and in the end on this house durability trumps energy efficiency in my mind hit that subscribe button below new content every tuesday and every friday follow me on twitter instagram otherwise we'll see you next time on the build show [Music] [Music] you

Channel: Matt Risinger

Views: 135,615

Rating: 4.936079 out of 5

Keywords: Matt Risinger, Build Show Network, The Build Show, Build, INSULATION

Id: N-X4_mbwP5I

Length: 7min 51sec (471 seconds)

Published: Tue Aug 31 2021