Radiant staple up insulation

Jane_6

I recently bought a house built in 1909 and had radiant heat installed on the first floor via staple up Pex tubing in aluminum pans in the basement. I am having a terrible time getting someone to insulate my system. Everyone has a different opinion and my plumber's only requirement/guidance is that it should be R30. I do not want spray foam so what is my best option? It seems like mineral wool but is it??? Here's how I got to that opinion: fiberglass has problems with airflow, off gassing and would be too thick at R30 for my 8" joists. Reflective stuff loses it's functionality after getting dust on it, rigid foam would have to be very thick to get to R30 and would be a pain to install with all the existing stuff in the bays. Blown in cellulose was proposed by two people but this just seems like it would be a total mess.

Details:

Uponor “HePex” crossed linked poly radiant heat tubing with oxygen barrier applied to sub-floor as a typical “staple-up” system including single groove aluminum heat transfer plates attached with zinc plated screws and sealed with 100% silicone. Tubing to be looped under a common end of joist bays in Basement.

The floors above are narrow width Fir and some Maple.

The basement joists are 2" x 8" and vary from 16" to 21" widths.

The joists have various other things going thru them like elec wiring and other pipes.

It's an old basement and obviously not tight but we are working on some air sealing down there. It is pretty dry.

Forced water system with baseboard in the other levels if the house.



Any guidance would be greatly appreciated. Thanks!

SWEI

Blown cellulose

can be wet-sprayed directly into the joist bay but it requires a really good applicator.



If you staple perforated Tyvek to the bottom of the joists you can dense-pack dry cellulose through a slit.

kcopp

there are...

other types of batt insulation. Denim is one. They also have more friendly fiberglass stuff now too that has no formaldehyde in it. Don't over think it. R-30 would be nice but if it will not fit in the joist bays they that will not work.

Eastman

mineral wool

Think about future maintenance; you probably want something that's easy to remove and put back in place.  Mineral wool can be cut more precisely than fiberglass, allowing for a significantly better fit, and it doesn't wick moisture like cellulose which can be a problem where the insulation is adjacent to the foundation.  Whatever you do, any basement air infiltration and moisture problems are really separate issues and probably need to be resolved before access is restricted by this project.



Try looking for mineral wool with a foil face.  Last time I checked they didn't have it in the correct width, but that was a long time ago.

Eastman

denim

I've heard denim is quite hard to install properly.

steveray

seal the bay

I was always told r-11 above heated space r-13 above un-conditioned (basement) whatever you use don't let the insulation touch the plates , insulate the end of the bays (rim or Ribbon joist) and make it as air- tite as possible. I've used bubble wrap (aluminum faced  duct wrap r5.4 $100 at local hvac supply 100'x4') stapled 2'' down from floor then filled the remainder with bat insulation r-13 (3.5'' thick) underneath, just don't use faced because of fire code. when I let the insulation touch the tubing it siphoned off the heat thru conduction. best that there is a 2'' air gap (sealed). believe me I found out the hard way.

SWEI

Huh?

insulation will not "siphon off" heat through conduction.  Bubble wrap is not very effective as insulation.

Mark Eatherton

Staple up insulation...

If you are using heat transmission plate, you typically DON"T want any kind of an air gap, because you want to enhance the conductive heat transfer (conductivity is the KING of heat transfer), and minimize any convective potentials (air heating).



If you truly have staple up or suspended tubing installed, you MUST maintain a 2" gap below the tubing with your insulation. If you can find foil faced insulation (a thing of the past) it will help reflect the radiant energy from the tubes back towards the floor where you want the heat to go, plus the convective energy. If you put the insulation in direct contact with the tubes, you will lose a significant portion of the output (convective) and the floor will underperform.



Curious about the recommendation to not use foil faced insulation from Steveray? Never heard of that, but then again I don't deal with ALL of the codes.



Bubble wrap in and of itself acts like 1/2" sheet rock... Been there, tested that, still have the data someplace in the Eatherton Archives from Red Rocks Community College.



ME

Jane_6

Heat transfer plates / contact with insulation

Thank you for all the input!  My system has the heat transfer plates so the tubes are not hanging down/suspended and as I understand it, having the insulation touch the tubes/plates is ok.  I don't need/want the 2" gap because I have the plates.



So Eastman wrote:

Mineral wool can be cut more precisely than fiberglass, allowing for a

significantly better fit, and it doesn't wick moisture like cellulose

which can be a problem where the insulation is adjacent to the

foundation.  Whatever you do, any basement air infiltration and moisture

problems are really separate issues and probably need to be resolved

before access is restricted by this project.



I hadn't thought about the moisture wicking aspect of the blown in cellulose application.  It would definitely be touching the exterior wall/foundation.  So, how would I resolve the basement air filtration and moisture issues?  Are you talking about air sealing, getting a tighter fitting basement bulkhead door, etc?  Should I be having some sort of barrier between the cellulose and the foundation wall if we go with that application?

Jane_6

Mineral wool experience

Have you had any problems with mineral wool?  Any guidelines for installing it?  

Gordy

Sealing the Rim Joist

The Rim joist is what your floor joists tie into on top of the foundation.



This area has a high heat loss, and can have infiltration. Use spray foam in the areas between the joists over the foundation. Or you can cut XPS and use great stuff to seal the edges of the XPS. Sealing this area prevents warm air currents from condensing on the cold surface of the rim joist. This holds true more so IF you leave a 2" gap between insulation, and tubing detail



As far as type of insulation, and how much in the rest of the joist bays. Cost may dictate type, along with application depending on mechanicals to navigate with in each bay.



Remember R 1 is 100% better than R 0. So anything you chose is better than nothing.



Spray foam has High R value, but can make a mess out of tubing plate detail, foam can expand between floor, and plates breaking the conduction link to the floor, along with mechanicals in the bay areas.



Fiberglass is probably the cheapest with the lesser amount of R value per inch along with convection currents with in the fiberglass its like a big air filter.



Denim pricey, but very dense product, and Green.



Rock wool is sorta between denim, and fiberglass.



There is another product called Roxul comfort batt wich will give you an R 30 with a 7.25 inch thick batt.

Eastman

what Gordy said

Adding: Foam insulation limits a walls potential to dry if gets wet, so it's very important that all other sources of water intrusion are resolved; leaking downspouts, improper flashing, improper grading, anything that promotes the intrusion of water into the wall assembly or increases the dampness of the foundation.  If your house has been retrofitted with exterior foam board that covers the rim joist, you may want to avoid foams with low vapor permeability in this location on the interior side.  Perhaps even foam in general.  (two vapor barriers can trap moisture)



"So, how would I resolve the basement air filtration and moisture

issues?  Are you talking about air sealing, getting a tighter fitting

basement bulkhead door, etc?  Should I be having some sort of barrier

between the cellulose and the foundation wall if we go with that

application?"



Yes to all.  The basement should be the primary air barrier  --that includes the rim joists, basement doors, other penetrations.  It's probably not practical to rely on the floor insulation to completely fulfill this function in the long term. 



Regarding the cellulose:  foam would be an excellent barrier between the cellulose and concrete.  Particularly if you don't have rim joists.  I'm not sure if it could be done another way.