txav8r's new barn construction (RV but could be boat)

[zipper]

That is a great R-value per inch. The insulation for the roof of our house is 8" of polystyrene laminated to OSB for an R-value of 40. (Stressed skin panels). Walls value is 26. Wishing I had your closed cell spray foam when I insulated the house 16 years ago.

 

[txav8r]

Oh no, I would love to have stressed skin panels for my home. When they built it, I am guessing they sealed every joint, so it is certainly better than the foam in the barn, overall, even if it's R value per inch is less. SIPs are so strong and efficient, it's the perfect structure.

 

[zipper]

Yes the roof is tight, but the 8" walls could be tighter. At the time I was trying to avoid needing a heat exchanger in an overly tight house. I used an infrared camera to find the weak spots as the houses timber frame went thru the drying cracking twisting period, can be 10 years long. I did recently find a cold spot where the roof timbers shift from the raised monitor section to a gable style, it needed a little more foam due to timber shrinkage.

 

[txav8r]

They did a really nice job. It was a mess and it's all cleaned up and looks great!

 

[Murf'n'surf]

Now it's time for the epoxy flaked floor, color matched to the coach!

 

[tdonoughue]

And some nice curtains on the back door...

<ducks and runs>

 

[txav8r]

I have the OSB up. What a challenge that was! The foam didn't go on even with overlap spots. So the OSB didn't lay flat. And I only had attach points at 5' and at the floor. It made for some creative efforts to get it to look half decent. Due to thicker foam, all my boxes are too deep. So now I am adding box extensions.

 

[BigN8]

Guys, I'm in the commercial roofing business and want to clear up your R-Value claims. Spray Polyurethane Foam is a closed cell version of a very common roofing insulation in commercial roofing called Polyisocyanurate. Both use urethane resin and Isocyanate mixed in a 50/50 ratio. The max R-Value of Polyisocyanurate or ISO is an R-5 per inch. It is the most efficient roofing insulation per inch in the industry right now. EPS or Expanded Polystyrene has an R-4/inch. I sell EPS as part of a LWIC system for roofing. LWIC = Light weight insulating concrete.

 

[txav8r]

Thanks for the verification on that @BigN8 .
Companies make all sorts of claims. With foam, it isn't the R value as much as the total seal, that creates a total enclosure that is both more comfortable as well as more efficient. I have a friend with a 2x4 stick built house with this sake closed cell foam, and it's almost like a refrigerator in terms of efficiency. And my hvac guy has a house that has icyenen (sp) foam and it IS like a freezer box or at least as efficient as one of those high dollar coolers that is boaters seem to like. Bottom line, the comfort and resistance to heat load is beyond the simple R value if you ask me, and it could just be a perceived comfort but it sure seems to be a great way to insulate.

 

[swatski]

@txav8r That interior treatment of yours looks fantastic!

Polyisocyanurate or ISO

Not to hijack, but wouldn't it be nice to have Yamaha inject some of that stuff into their hulls!

--

 

[BigN8]

Thanks for the verification on that @BigN8 .
Companies make all sorts of claims. With foam, it isn't the R value as much as the total seal, that creates a total enclosure that is both more comfortable as well as more efficient. I have a friend with a 2x4 stick built house with this sake closed cell foam, and it's almost like a refrigerator in terms of efficiency. And my hvac guy has a house that has icyenen (sp) foam and it IS like a freezer box or at least as efficient as one of those high dollar coolers that is boaters seem to like. Bottom line, the comfort and resistance to heat load is beyond the simple R value if you ask me, and it could just be a perceived comfort but it sure seems to be a great way to insulate.

I had a spray polyurethane business in the early 2000's and did a few custom homes with 1lb density foam. We actually had a problem with a few of them by making them too "tight". The humidity was too high and the windows started sweating. Created a potential mold problem. We found out later through a few more of these that it's a delicate balance between air barriers and HVAC tonnage. If you seal the house too tight and have too much AC the AC won't run enough and won't dry the air.

 

[txav8r]

I had a spray polyurethane business in the early 2000's and did a few custom homes with 1lb density foam. We actually had a problem with a few of them by making them too "tight". The humidity was too high and the windows started sweating. Created a potential mold problem. We found out later through a few more of these that it's a delicate balance between air barriers and HVAC tonnage. If you seal the house too tight and have too much AC the AC won't run enough and won't dry the air.

That is very true, and both of these guys I am talking about have and outside fresh air return supply line that is triggered by humidity of all things, just like you mention. I think it is even code in some cities to have that fresh air return. Let's face it, having a drafty house vs a tight house, just to have the a/c run enough is money being thrown away. If I have to pay to have to condition more air than necessary, just to dehumidify, why not incorporate a dehumidifier? I will also add, that a tight house doesn't take on near as much outside air humidity as a drafty house. You are absolutely right that there is a balance, but there are ways to achieve that balance without running an a/c continuously. My house is 6" walls, with tyvek wrap, R-21, the roof is protected by Coolply Radiant barrier, continuous ridge vents, Hardi perforated soffits, 4 huge gable vents (that are blocked with foam board because I have too much ventilation), R-40 level blown in fiberglass insulation, that sets the tone for the two Trane Geothermal indoor (installed in attic) compressor sections that are supported by 5-250' deep geothermal closed loop wells. My units don't run near as much as conventional units, and I do not have a fresh air supply. The humidity level in the house is very comfortable summer and winter, but the spring and fall can be a little humid, when the units don't run at all, due to the house being well insulated. So we will turn on the a/c just to remove humidity. But I suspect all of us in north Texas, have that same issue at that time of the year. It is the same time of year that you can't decide whether to run the a/c or the heat! We don't have programmable thermostats and have to make a decision which is active. And the reason is that it cost more to drop the temp and bring it back up, in a well insulated home, than it does to maintain the temp 24/7...the exception for us, is if we are going to be gone for more than a little less than 72 hours, then raising it 4 or 5 degrees can be a savings. But we have pets, so it isn't often we will do that. Because a geothermal home is pretty cheap to cool and heat. I have not purchased a dehumidifier, and haven't felt the need, but if I built another house, I would definitely foam it. A controlled humidity level between 35-55% is ok. You may see condensation on the inside of windows with greater than 40% humidity in winter months...IF you don't have thermally broken window frames and very good insulated glass. We have those too, argon gas filled and LowE coated, but the bad news is that argon dissipates before the seals fail and I think the argon is very beneficial. Nate, I think a gathering is a good place, beer in hand, to chew the fat and discuss subjects just like this. I have always been interested in energy efficiency and enjoyed it. And you guys that put together systems and know the benefits are great at what you do!

 

[txav8r]

Forgot to say...I finished the outlets and switches!!! I am done except for painting the OSB (if the wife decides we can paint it to match), and hanging an exterior light.

 

[txav8r]

It's all finished except for painting the OSB! All lights and hardware installed!

 

[txav8r]

I should update a little. I’m looking st mini split heat pumps to stabilize the humidity and temperature in the RV barn. The foam isn’t holding the temps above freezing in the winter or stopping the heat load in summer. So I may do it. Thoughts? I was told a small unit would do the trick. Now I’m told it needs 3 tons.

 

[Hector]

I should update a little. I’m looking st mini split heat pumps to stabilize the humidity and temperature in the RV barn. The foam isn’t holding the temps above freezing in the winter or stopping the heat load in summer. So I may do it. Thoughts? I was told a small unit would do the trick. Now I’m told it needs 3 tons.

Minisplits are the way, if I could do my house all over I would go this route but with ducted indoor air handlers.
Use a reputable company like Mitsubishi or Daikin. We install mostly Mitsubishi. It’s impressive how you can heat in -5 degrees with no auxiliary heat strip..

 

[tdonoughue]

Without significant R value in the walls (I forget what the foam you put in is, but it can't be much versus traditional insulation) and with no R value to those doors, I think you are basically going to be heating/cooling the greater Dallas area. So I am not surprised at 3 tons. You will have better humidity effect than you will heating/cooling--but that you can also get with a dehumidifier...

I am not presenting much of a solution for you here. Sorry about that. But I think that is just the nature of the beast you built--they aren't much for heating and cooling.

 

[txav8r]

Without significant R value in the walls (I forget what the foam you put in is, but it can't be much versus traditional insulation) and with no R value to those doors, I think you are basically going to be heating/cooling the greater Dallas area. So I am not surprised at 3 tons. You will have better humidity effect than you will heating/cooling--but that you can also get with a dehumidifier...

I am not presenting much of a solution for you here. Sorry about that. But I think that is just the nature of the beast you built--they aren't much for heating and cooling.

Actually, the barn is tight, and those big doors are insulated steel and do have an R value, although I don’t know what it is. Even the entryway walk door is insulated. The R Value of the foam is R7. It is about an inch and a half. It is thickernin the ceiling as it was ajoce them and harder to layer evenly, so when finished they told me it ended up thicker. And the quantity of product used figured to be more. Be that as it may, the heat loss or gain rate in the building is good, but it doesn’t prevent it from dropping to freezing in long stretches below freezing. Nor does it keep the inside from climbing in the summer eventually. My big issue, is that once the temps climb by late afternoon in a day over 100F outside, in the 90’s inside, and then at night, the temp falls outside, but don’t drop much inside and the humidity is trapped in the building. So I need to condition the air. The question is, could I get a inside temp window of 40 to 80 year round out of a smaller split, or do I need to get the 3 ton?

 

[Bruce]

Mel,

I plan to get some heat load calculations for my 30x40 Quonset hut pool project next week. If you have time to wait they may help you.

My house is built from 6.5” thick SIP panels with Low-E windows and very tightly sealed with the exception of French doors that I have left leaky for air exchange. We heat and cool 3600 square feet with a 4 ton unit that runs infrequently.

When the power is off on a summer day we gain about half a degree per hour.

When a ice storm hit we lost power for four days. The inside temp had been around 75 degrees when the power went off. We had a 14,000 btu propane heater running. Four days later the inside temp was 69 degrees. A little over a ton of heat had slowed the drop in temperature but was not enough to hold the temperature.

My house is much better insulated than your building however it still has gains or loses temperature over time.

You may be able to determine that a smaller system would maintain the temperature that you desire however if you want to cool or heat it to 75 to work in there then I suggest going with a larger system which will make that transition faster.

 

[txav8r]

Mel,

I plan to get some heat load calculations for my 30x40 Quonset hut pool project next week. If you have time to wait they may help you.

My house is built from 6.5” thick SIP panels with Low-E windows and very tightly sealed with the exception of French doors that I have left leaky for air exchange. We heat and cool 3600 square feet with a 4 ton unit that runs infrequently.

When the power is off on a summer day we gain about half a degree per hour.

When a ice storm hit we lost power for four days. The inside temp had been around 75 degrees when the power went off. We had a 14,000 btu propane heater running. Four days later the inside temp was 69 degrees. A little over a ton of heat had slowed the drop in temperature but was not enough to hold the temperature.

My house is much better insulated than your building however it still has gains or loses temperature over time.

You may be able to determine that a smaller system would maintain the temperature that you desire however if you want to cool or heat it to 75 to work in there then I suggest going with a larger system which will make that transition faster.

Makes sense @Bruce . My house is efficient via geothermal units but my heat load is higher than yours as it is not SIP construction. The barn is certainly a greater heat load. I have no desire to pay to heat cool the outdoors. But I want to preserve the coach and make the interior barn comfortable in extreme conditions outside when I am in there. It’s nit a workshop per se, but...

Seems pretty reasonable and simple to add a single unit in the 36,000 btu range and let it be what it may. It will get me what I am lookin for I think.