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-   -   New home construction.. Small attic minimal insulation (http://www.diychatroom.com/f103/new-home-construction-small-attic-minimal-insulation-146686/)

Robert95z 06-11-2012 02:15 AM

New home construction.. Small attic minimal insulation
 
Im currently getting a house built but i was kind of worried about the insulation that comes standard. I live in Houston, TX and it is very hot.

Insulation: R-13 Walls and Floors, R-19 sloped walls, R-22 under platforms, R-30 flat ceilings.

The contruction of the 1 story home leaves very very crawl space in places like the living and master because of the recessed ceilings. I figured I would add my own insulation, but now im worried if there is enough room.

I was planning on just blowing in insulation all over but now looking at the construction, i dont think i can even get to most off the edges to install rafter vents.

Also, would you guys recommend a radiant barrier (tech sheild)?

This is my first home, I've never done and real DIY's but im very mechanically inclinded and believe I can take on just about any job.

But i need some professional advice on what you guys would do.

goosebarry 06-11-2012 04:17 AM

Quote:

Originally Posted by Robert95z (Post 940750)
Im currently getting a house built but i was kind of worried about the insulation that comes standard. I live in Houston, TX and it is very hot.

Insulation: R-13 Walls and Floors, R-19 sloped walls, R-22 under platforms, R-30 flat ceilings.

The contruction of the 1 story home leaves very very crawl space in places like the living and master because of the recessed ceilings. I figured I would add my own insulation, but now im worried if there is enough room.

I was planning on just blowing in insulation all over but now looking at the construction, i dont think i can even get to most off the edges to install rafter vents.

Also, would you guys recommend a radiant barrier (tech sheild)?

This is my first home, I've never done and real DIY's but im very mechanically inclinded and believe I can take on just about any job.

But i need some professional advice on what you guys would do.

This sounds like a state-of-the-art design for 1970s. Why are you building this house now?

Walls R-13: That is 2 x 4 construction. They should be using 2 x 6. The incremental cost is minimal if done while building the house. That will give you R-19. I don't think 2 x 4 exterior walls is even legal here for new construction.

Sloped Ceiling R-19: if the roof uses 2 x 6 then you won't get the full R-19. Those sloped roof cavities need baffles to properly vent the attic. If they use the cheap styrofoam baffles you find at the big box stores,, one of two things will happen: The effective R value will be reduced to R-17 because the insulation is compressed or more likely the baffle will collapse and screw up the venting. The cheap baffles are just deep enough to meet minimum venting requirements. There also kind of short. You want the baffle to extend at least 12" above the ceiling rafters, so the soffits don't get filled when adding more insulation. Also have them add 1 1/2" XPS to the interior slope ceilings that will add an additional R-7.5 and you won't miss the space. I just retrofitted our sloped ceiling and got up to R-28 using a combination of batts, XPS and radiant.

Flat Ceiling R-30: 2 x 8 ceiling rafters. Add batts or blown in to recommended R value (R-49 or R-60). You said that the space was tight, so you might want to have them do it before putting on the roof. If you do it after there are extension poles that can be used to get the blown-in into far tight corners.

I haven't research or worked on crawl spaces, Hopefully someone else can help.

Yes you want a radiant barrier, but it is a lot easier to have installed with the roof.

You also want a vapor barrier. I believe they go on the outside in Houston, because it's hot and humid, so you want to stop the humidity from migrating from the outside into the walls. Again, I'm in snow country so can't help.

Robert95z 06-11-2012 04:52 AM

Your reply has me having some serious buyers remorse..

Ive already signed the dotted line and they have $1000 in earnest money... I already had cold feet, but now im about to have a nervous break down. :eek:

The 1st home we were going to build came standard with R38 ceiling and tech sheild, but came out a little over budget.. Now i feel like I should have just went with them... :(

joecaption 06-11-2012 06:23 AM

http://www.energystar.gov/index.cfm?...sulation_table

goosebarry 06-11-2012 02:57 PM

Quote:

Originally Posted by Robert95z (Post 940762)
Your reply has me having some serious buyers remorse..

I looked up the 2009 IEEC values for Houston (zone 3) and I have good news, the minimum insulation values are:
Ceiling R-30
Wood Wall R-13
Floor R-19
Crawl space wall R-13

So everything is in compliance. You might want to note Table 402.1.1, the 2012 IECC ratchets up minimum prescriptive insulation levels in several climate zones:
•In climate zones 2 and 3, the minimum ceiling R-value has been increased from R-30 to R-38.
•In climate zones 3 and 4 (except zone Marine 4), the minimum R-value for above-grade walls has been increased from R-13 to R-20 (or R-13 with an additional layer of R-5 continuous insulation).

I'm not sure what version of the code Houston uses and I don't think the IRC has adopted the 2012 IEEC recommendations yet.

You still want to make sure you have the proper vapor barrier and maybe get your contractor to install the radiant barrier.

Maybe you could install organic solar blockers, that block the sun in the summer and let it shine through in the winter.

Feel lucky your not where I live. The minimum wall R-value just increased to R20+R5.

goosebarry 06-11-2012 03:01 PM

Quote:

Originally Posted by joecaption (Post 940769)

Here is a better read for new construction:
http://www.energycodes.gov/training/...esidential.pdf

Robert95z 06-11-2012 11:02 PM

Thanks for the info guys... Im pretty sure im going to back out on this house. I called the sales person and they said if I really want to back out they will return my earnest money. Im leaning back towards my first gut instinct of a chesmar home. It comes with more standard, better features, but is in a MUD tax district so was more expensive monthly. But about the same selling price. Here are the stats for the ches mar..

R-15 wall insulation, living areas (vs 13)
R-38 blown-in attic insulation, living areas (vs 30)
R-22 insulation on sloped ceilings, at top plates per Energy Star specs, living areas (vs R19)
Energy efficient Tech Shield® or equivalent radiant barrier roof decking
High Efficiency 16 SEER HVAC system with Trane condenser and 80% AFUE Trane furnace (vs 14 seer)

I think im going to switch builders. I wont lose anything, but my payment will be $100 more a month, which isnt bad I suppose.

Gary in WA 06-12-2012 01:01 AM

You are under the '09, read all your local amendments; especially pp. 11: http://documents.publicworks.houston...sidential.html

The switch will give you better (denser) wall/sloped ceiling insulation, which will help against convective loops: http://www.diychatroom.com/f98/bigge...ulation-90438/

Here is a paper on your local best building practices:http://www.buildingscience.com/docum...=houston+texas

After reading, click on the links with "hot-humid" in the list of titles near the end, good reading!

Gary

goosebarry 06-12-2012 01:10 AM

Quote:

Originally Posted by Robert95z (Post 941428)
Thanks for the info guys... Im pretty sure im going to back out on this house. I called the sales person and they said if I really want to back out they will return my earnest money. Im leaning back towards my first gut instinct of a chesmar home. It comes with more standard, better features, but is in a MUD tax district so was more expensive monthly. But about the same selling price. Here are the stats for the ches mar..

R-15 wall insulation, living areas (vs 13)
R-38 blown-in attic insulation, living areas (vs 30)
R-22 insulation on sloped ceilings, at top plates per Energy Star specs, living areas (vs R19)
Energy efficient Tech Shield® or equivalent radiant barrier roof decking
High Efficiency 16 SEER HVAC system with Trane condenser and 80% AFUE Trane furnace (vs 14 seer)

I think im going to switch builders. I wont lose anything, but my payment will be $100 more a month, which isnt bad I suppose.

The upgrades will pay for most of the $100 each month. Upgrading to a high efficiency furnance wouldn't pay for itself in Houston.

Side question: Isn't the MUD tax paying for your sewer and water or is like the SRP levy my parents pay in Arizona. Their house is in the SRP district, so they pay a monthly fee for irrigation and power eventhough they don't irrigate and they get their power from the city.

Robert95z 06-12-2012 01:27 AM

Thanks for the links GBR.. I'll take a look

goosebarry, yes mud is a tax for getting water/wasterwater to/from the subdivision.

"A Municipal Utility District (MUD) is a political urban subdivision of the state authorized in Chapter 55 of the water code to provide water and wastewater service to a specific region. In order to accomplish that goal, the MUD may purchase or construct and operate facilities that serve the region; it may issue bonds to finance the purchase or construction of such facilities"


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