Sound insulating the doghouse

[wayward]

In own a 2007 Mirada class A motorhome. And in my coach the only thing between me and a howling V10 was fiberglass and carpet. I was looking for a way to significantly reduce the noise and heat transmission through the doghouse or tunnel. Here is what I did.

Shopping list:

6 X 2" elevator bolts in 1/4"
6 X 1/4 nylon lock nuts
6 X 1/4" fender washer
1 sheet of metal lathe with ridges.
1 package of Roxul Safe and sound insulation. (Comes with 12 pieces)

You can buy everything at Lowes except the Roxul which Home Depot carries. Some Lowes are starting to carry Roxul as well.

I removed the doghouse and laid it upside down and laid to pieces of Roxul side by side in the Dog house. that filled the doghouse perfectly. I then trimed it to fit with a serrated bread knife or a saws all blade. On top of the 3" thick Roxul I laid the metal lathe I believe that it was 28" wide. I trimmed the lathe to length and clipped the corners to fit. I used tin snips and a metal cutoff tool using an abrasive disk. I then drilled the 6 holes through the top of the doghouse. I inserted the elevator bolts though the carpet, fiberglass, insulation, and metal lathe. As the bolts are 2" you will need to press down on the lathe firmly to attach the washers and nuts. That's it! I still had space between the lathe and the engine intake. I had to press down more to re-insert the doghouse bolts and that's good.

Test drive impressions were amazing. I hope for some relief from the noise and I got more than I could have hoped for. Conversation and movies are much easier to hear now. I believe that the heat should be lessened significantly also. Total price was just under $50. I am so pleased with the results and so is my wife.

Roxul is made from basalt and slag and is pure rock. Melting point is over 2200 degrees Fahrenheit. Google it it has a lot of amazing properties but remember that Roxul comes in two forms. One is for temperature insulation and one is for sound. I recommend the Safe and Sound which is designed to stop noise.

Jonathan

(Sent from my phone so forgive any typos please)

[mark0224]

Used foil backed insulation from hardware store like lowes
Shop Reflectix 25-ft x 24-in Reflective Insulation at Lowes.com

you might want multiple layers to kill noise, also good quality duct tape and some small machine screws with large body washers . Make sure you use enough screws so foil insulation doesn't sag and wherever you put a crew put duct tape also duct tape along all the edges wrapping around the foil.

[wayward]

I looked at that material. But it was only rated to 140 degrees. And even with multiple layers it wasn't as thick. The Roxul is a full 3" thick. Not the 1/2" layers.

[mark0224]

It may not be as thick but material like this is what they use in the dog houses. Did you look at the specs for Roxul it has formaldehyde in it not good.
Roxul Safe 'n' Sound 3 in. x 15-1/4 in. x 47 in. Soundproofing Stone Wool Insulation (12 pieces / package)-RXSS31525 at The Home Depot

[wayward]

I see your point. But then again formaldehyde is used in many places. Including plywoods. I'm am not sure if they have completely gotten away from its use. I agree that it isn't good stuff. I know that the demonstrators use a blow torch on the product. They don't wear a mask. I am glad you pointed this out.

[OldCoot]

Originally Posted by wayward

...in the specifications area it states that it is a Formaldehyde free product.

To the contrary, the spec says "Formaldehyde Free No".

But, so what? It's in the doghouse and no one is breathing or touching it. Formaldehyde is in a lot of products.

[wayward]

Sorry I corrected my statement. And yes I still believe it safe as they sell the product to be used in the walls of your home. In fact I would refer to the company website at www.roxul.com when making you decision. The safety section and FAQ section I found helpful.

[camaraderie]

Wayward...sounds like a great improvement and cheap to do. Question...how did you position the 6 bolts? If you had to do it again, would you use more bolts? If you can't post a picture...maybe just post some x's in a pattern so that it is clear. Thanks for the good tip!

[wayward]

I eyeballed the bolt locations. I put them near the top and bottom and sides to support the lathe. The ridged lathe is pretty strong and when the Roxul is sandwiched makes a solid unit. I bought 8 bolts but found that 6 were more than sufficient. I put 3 across the bottom and 3 across the top. One one each side with one centered. I held the flat heads with some pliers as I tightened the lock-nuts with a ratchet. In the end it was nice and snug. It strengthened the fiberglass. The doghouse doesn't have that hollow sound now when you hit it with your hand. I'll try to post some pictures in the next couple of days.

[wayward]

If you were cool and had friends with class A's. You could drop the cost a lot. You will have enough lathe and Roxul for 3 MH. Actually if you bought 2 sheets of lathe and the hardware you could do 6 MH.

Roxul one package. $42. (12 pieces). You need 2 per MH

Lathe $7. Will probably do 3

Hardware. $8 ish

So split the cost and everybody wins.

[wayward]

Tunnel underside

[camaraderie]

Ahhhh...so that's how you did it. A picture is worth .....
Thanks!