Hi,  I am looking at potential solutions, retrofits, and renovations to a home we have recently purchased.  The home was built in the early 1950s and is about 2400sq-ft all one level brick home with slab on grade construction in Virginia.  The home was built with a radiant floor heat system that looks to be steel or iron pipes embedded in the concrete.  This system has been abandoned some time ago due to leaks (no surprise).  The current heating system is an in-attic natural gas furnace with ducting in the attic and registers in the ceilings of each room.  The duct work was built for a central AC system and it works fairly well for cooling but even with ceiling fans, the heat is less than desirable as it is always cold at ground level regardless of the temperature setting.

We would like to explore options for improving the heating system and comfort of the house.  Step one is going to be improving the insulation in the attic and around the duct work and we will be replacing the original single pane windows and storms with something more efficient (and less rotted).  The second step is to get heat back at the floor level and this is where we need the most advice.  The floors in the house (parquet and linoleum) need replacing in every room except for the bathrooms (ceramic tile) and the foyer (stamped concrete).  We have not examined what is under the flooring to determine the thickness of the subfloor (if any).  It is likely that the thickness of the solution chosen will be an important consideration to avoid having to re-engineer all of the doors and thresholds in the house.

Anyway, the options appear to be the following:
1) Attempt to repair existing system--Probably NOT repairable unless someone develops a magic goo that will descale and seal the existing pipes and has good heat transfer properties.....
2) Hydronic radiant heat retrofit on top of existing slab:
     ---2a) Use a router to groove existing subflooring and install PEX tubing
     ---2b) Install pre-fab product such as Warmboard or Infloorboard
     ---2c) Thin pour slab
3) Install hydronic baseboard heat system
4) Buy more down-filled slippers


We are interested in any advice available on:
--which products to use,
--how best to design a sytem with multiple manifolds/zones to reduce the number of runs required to return all the way across the house,
--how/where to pass PEX through existing walls (plaster & lattice)
--How best to work around large brick interiror walls with fireplaces, the stamped concrete floor in the entryway, and the tiled floors in the bathrooms.
--Flooring optins to go on top of any of the flooring solutions above

Thanks!

Insulating the slab edge with 2" of foam on the exterior of the stem wall at least to the frost line will lower the heat load and improve the under-foot comfort somewhat.

Unless you know for sure that the slab is insulated to at least R5 (unlikely circa 1950, but a few exploratory drill holes can tell), cutting in floor radiant probably isn't the right approach, but radiant-ceiling might be, and you can air-seal the ceiling at the same time.  Radiant ceiling probably easier and cheaper than a Warmboard or thin-slab over additional foam approach, and won't reduce headroom.

If the slab is uninsulated, even R2.5 of XPS under the the new finish floor can be a noticable comfort improvement (but nowhere near as cushy as radiant floor.)

If the ducts and air handler haven't been pressure-tested and air-sealed, it's probably a good idea.  If the ducts are uninsulated or have R values less than R6 there's room for improvement there too. 

With ducts in the attic it might be worht pursuing an insulated roof deck/unvented attic approach to the insulation improvements, but the expense of going high-R that way can be daunting compared to just insulating the ducts and going R-50 with cellulose on the attic floor.

Odds are the 1950s vintage stick build has R8 or R11 batt insulation in the walls, and it may not have anything at all.  If you can verify that the brick veneer is has at least an inch of channel between the studwall wall and the masonry, and that there is sufficient roof overhang to keep the bulk of rain moisture off the brick, a retrofit installation of blown cellulose in the walls is likely a good investment, as it will reduce air infiltration as well as insulate.

All heating system designs start with a good room-by-room heat loss calculation, which may point you toward some options over others.

Thanks Dana1.

Your reply reminds me that I should provide a bit more information.

--The duct work is airsealed but not insulated. This is going to be my first step as even if the duct work is just used for AC, there are huge losses here in the attic.
--The roof has zero overhang to keep rain off the brick. This also means that there is no soffit of fascia venting in the attic. There are gable vents at the ends of the roof but that is it.
--I would like to stay away from radiant ceiling for the same reason that I would like to get away from the forced air through ceiling vents---The warm air does not warm up the room or the floors effectively....
--The slab is likely uninsulated but we won't know without drilling some holes. Same goes for the walls, we don't know what is in them yet...

Depending on how accessible the bottoms & sides of the ducts are, you may be able to kill 2-birds with one stone by sealing/insulating the duct work with 1-2" of closed cell spray foam (at about a ~1.20 per square foot per inch, if you buy 600 board-foot TigerFoam or FomoFoam etc type kit ). Fiber insulation on metal ducts can lead to condensation issues on the ducts, especially in vented attics in humid summertime climates such as VA. An inch of cc foam is about R6, but it's difficult to be consistent. Air handlers seams are often more easily sealed with 2" FSK tape (aluminum tape designed for duct applications). Duct mastic is also cheap & easy, but shouldn't be used on air handler panels needed for service access.

Even without soffit venting you'd be required to provide a vent cavity between fiber insulation and the roof deck at the soffit end. If you don't have sufficient depth there, an inch of cc foam against the roof deck would allow you to safely fill it right up. (R50 would have an initial depth of ~16" from ceiling lath or gypsum on up.) If the roof pitch is low and limiting insulation depth severely, that can limit the overall performance severely, since the thin edges will dominate the heat gain/loss of the whole assembly. In many ways going with an unvented air-tight attic design is preferable, but there's a lot to consider before taking that step. Splitting the total-R between the roof deck and the attic floor is legitimate, and makes the attic a semi-conditioned space in the middle of the thermal boundary, but it has to be done in such a way that neither wood in the attic nor the roof deck accumulates seasonal moisture (which is the primary reason for venting attics), which will involve at least some amount of $pray foam. But it's easier to fully air-seal the top of the house at the roof deck when you have 1001 electrical, plumbing & duct penetrations at the ceiling below the attic floor. Ducts in the attic above the insulation are a bad idea handed down from the days when energy was cheap and climate change wasn't on anybody's radar. But there are still ways to make the best of it when that's what you're handed.

Radiant ceiling is more effective at warming up the stuff below it than you might think (including the floors). It's a HUGE comfort improvement over ducted-air or fin-tube baseboard solutions, and has quicker response times than slab-radiant floors. Across 8-10' of air the primary heat transfer mechanism is radiation, and a radiant ceiling heats up the tables/chairs/floors/humans/pets below it before it heats up the room air. But lo-temp radiant baseboard/euro-panel type radiators are also pretty cushy, and might be cheaper/easier to implement if you can figure out the plumbing chases for the tubing. With a radiant ceiling you can pretty much keep all of the heating system distribution plumbing in the attic and bury it in insulation, which may prove simpler in the end- it just depends.

Where are the return air grilles located. You do not want to attempt to repair old radiant. You may want to consider baseboard or wall panel radiators. Your existing force air system may be modified to improve comfort levels. The key to any force air system is proper design and return air is critical for proper performance.

Dana, thanks for the advice on the CC foam for insulating the duct work. I was thinking of using 1 1/2" OR 2" rigid foam as the duct work is all flat and easily accessible.

The roof is a good pitch so there is about 6 feet of height in the attic and the center of the attic has floor decking on it for the full length of the house (~100ft) with the 3 feet or so where the roof is the lowest exposed with the original insulation visible. There is not much there--maybe 6" at most and it has surely settled/compressed over time. With the amount of usable space up in the attic (probably 1500+ sq-ft), it would be nice if it were semi-conditioned space so bringing the attic inside the envelope is an appealing thought.

More information on the roof:
The roof decking is nice 15" lumber with maybe 3/16" gaps between the boards. The roofing itself is asbestos composite shingles and is in pretty good shape with the exception of some loose shingles along the ridge where they are only glued down and not nailed like the rest of the roof.

ACWizard:

The return duct is a single huge ceiling vent in the middle of the house. It is probably about 5-feet by 6-feet and has a decorative grille. When I first saw it, i thought it was a whole-house-fan.

There are a couple of radiant floor systems available for retrofitting failed 1050's radiant floor heating systems. One radiant floor retrofit for overpours, one is a surface mount and the other option is to install European style panel radiators. All retrofit radiant floor heating systems require a room-by-room heat load analysis performed by an experienced designer using software made for the task.

Once you have the load, the various options fall into place. Naturally you will need a boiler, sized to the load and an indirect water heater. You may also opt for a condensing tank type water heater with a sub-assembly for space heating.

As for insulation, Dana always has it covered, but if you want carpet and find the panel radiator option appealing, the right carpet and pad can be as good as some purpose built insulation. Lucky to have AC overhead instead of a worthless whole-house fan!

Posted By jorshw on 30 Aug 2011 03:12 PM
ACWizard:

The return duct is a single huge ceiling vent in the middle of the house. It is probably about 5-feet by 6-feet and has a decorative grille. When I first saw it, i thought it was a whole-house-fan.

Yikes! That's huge- better be sure that's air-tight, and has sufficient insulation over it-  you don't need a 30 square foot hole in your ceiling insulation!

Yeah, it is massive and uninsulated so a huge heat loss....

Right now, we are leaning toward bringing the attic into the envelope of the house which would kill several birds with one stone (air seal, insulate, plus gain a huge semi-conditioned space for storage). It sounds like doing spray-foam would be the best approach along with sealing off the gable vents and installing an HRV system.

Thoughts?

Posted By BadgerBoilerMN on 30 Aug 2011 05:29 PM
There are a couple of radiant floor systems available for retrofitting failed 1050's radiant floor heating systems. One radiant floor retrofit for overpours, one is a surface mount and the other option is to install European style panel radiators. All retrofit radiant floor heating systems require a room-by-room heat load analysis performed by an experienced designer using software made for the task.

We really like some of the European Panel radiators so this may be a good alternative.  The floors are in rough shape and could use replacing anyway which is probably what had us thinking heat in the floors as we have to tear them up regardless.  Not sure how we would go about running the supply and return lines for Panel radiators in an aesthetically pleasing manner without major renovations to the walls (plaster over lattice with brick exterior) or by using vertical floor-to-ceiling style radiators so we can hide the chases in the attic. 

Posted By jorshw on 31 Aug 2011 12:37 PM
Yeah, it is massive and uninsulated so a huge heat loss....

Right now, we are leaning toward bringing the attic into the envelope of the house which would kill several birds with one stone (air seal, insulate, plus gain a huge semi-conditioned space for storage). It sounds like doing spray-foam would be the best approach along with sealing off the gable vents and installing an HRV system.

Thoughts?

How deep are the rafters?

Are you re-roofing any time soon?

A flash-foam of closed cell on the roof deck (1" nominal) is sufficient to protect the roof deck from interior moisture drives, and would allow to do a wet-sprayed-in-netting rafter cavity fill to bring the R up to something decent.  Most wet-sprayed fiber is fire-rated as an inition barrier for the foam at 3" or more, which means you need not add OSB or gypsum to the interior. But if you're going to do that anyway, a dry-blown approach would aslso work.  For an analysis of the flash'n'fill approach, see:

http://www.buildingscience.com/docu...of-systems 

Your winters aren't warm enough to use an all open-cell foam approach, but an inch of closed cell is enough.  See the tables 3 & 4- the winter-climate profile closest to yours would be Kansas City, of the examples given.  The IRC 2009 specifies R15 as the minimum for the foam layer in your climate zone (4A) but that's clearly too stringent, per the analyis in that document. R6 is enough, but R12 is better.

If you're re-roofing, it's cheaper to go with rigid-foam above the roof deck, with an OSB nailer deck (through-screwed the rafters) on which to apply the new roofing, which has the significant additional benefit of a decent insulation-break over the thermal-bridging of the rafters.  Using the IRC guideline of R15, that could either be 2.5" of iso, 3" of XPS or 4" of EPS.  A 2x8 rafter has an R value of about  R7, robbing performance from the R30-ish insulation between the rafters (assuming R6 of cc foam + R25 of batt or blown fiber), but with R15 on the exterior, that becomes R22 at the rafters, and you can use cheap fiber between the rafters.

Inspect carefully at the soffit end of the pitch- if the cavity between the brick &  studwall is currently vented to the attic, you'll have to cut exterior vents into the mortar on the exterior for that cavity to continue to perform it's function.  It may already have a bottom-course weep holes and top-course vents in the brick, or may have at one time, sometimes filled in during re-pointing.  If not, adding them yourself is usually a good idea, as it purges moisture soaked up by the brick to the exterior rather than raising the humidity in the stud cavities. Sun on rain soaked or even dewy brick creates a HUGE humidity drive toward the interior, but with a top & bottom vented cavity the wood & insulation in the studwall is spared the brunt of it.  In air-conditioned homes an unvented masonry cavity often results in condensation or mold growth on the interior side of the stud bay (in your case, on the lath.)

On the gable ends you can use either open cell foam, or a blown/sprayed fiber-fill.

ERV would be better than HRV in your climate, as it would lower the latent load to the air-conditioning somewhat.  It's unlikely that you'd be able to make the place so tight that you'd absolutely need it, but ventilation by design rather than accident is still key to guaranteeing good indoor air quality.

BTW: If the AC has been keeping up even with uninsulated ducts in the attic, it'll likely be 4-5x oversized for the cooling load after you've tightened up the house and improved the insulation of both the ducts & attic (especially if you insulate the roof deck.)  This may result in duty-cycles too short to provide good dehumidification.   Monitor the indoor humidity- if it's staying above 60% most of the summer you may have to take other measures, such as a small ductless mini-split heat pump air-conditioner with a dehumidification mode, or larger-sized room-dehumidifier set up to drain to a sink or sump, etc.  Above 65% relative humidiy is uncomfortable, but above 60% is unhealthy.  (Above 50% is unhealthy for people with dust-mite allergies.)

Posted By Dana1 on 31 Aug 2011 02:26 PM

How deep are the rafters?

Are you re-roofing any time soon?

The rafters are 6" deep.

The roof is the original asbestos/composite shingles and they are in good condition.  The only trouble spots are along the ridges where the shingles are only held on by adhesive so they are prone to coming off after nearly 60 years of use.  We were planning to simply remove the side-lapped shingles along the ridges and replace them with a copper cap to match the valleys, flashing, gutters, and downspouts.  This should hopefully keep the roof serviceable for many years to come.

Additionally, getting an EPA approved team to come remove and dispose of the old roof is big $$$ that we hope will be better spent elsewhere.


I'll have to check to see if the cavity between the brick and studwall vents to the attic.  I suspect it does as I did not notice any exterior venting or weep holes.

With 2x6 rafters you might go with 2" of 2lb foam (R13) and R13 unfaced batts (R13) with OSB or gypsum on the sloped ceiling. Center-cavity it would be R25 ish.

If the inspectors insist on R15 per IRC 2009 you can go with 3" of the higher-perm/lower-R 2lb density Icynene product (MD-R-200) which is R5/inch, and meets the R15 spec. That would leave ~2-1/4" of space, into which you would compress unfaced R11 or R13 batts, a thickness at which the would perform at ~R8.5-R10, or put up the OSB/gypsum and dry-blow it full of cellulose for ~ R8-9. Either way you're at ~R25 center cavity, and haven't created a roof-deck rot situation. With thermal bridging factored in it'll still come in over R20.

Insulate all the way down to the top plate of the studwalls with foam. You may have to pull the attic floor insulation back to do that, but the junction at that top plate is a critical likely place for air leakage, and if the leakage path involves pulling humid masonry-cavity air in there's some potential for localized moisture problems. But also insulate the attic floor to the extent possible- even if it just under attic floorboards & 2x8 floor joists, fill 'er up with blown cellulose, but air seal as many of the electrical, plumbing, and flue penetrations as possible before you do, as convection currents can become a thermal bypass for the attic-floor insulation, limiting it's effectiveness.

Ideally you'd end up north of R40 for a combined whole-assembly R, with all thermal bridging accounted for, but even R30 (whole-assembly) would be pretty good. Given the huge hole represented by the return duct grille I'd be surprised if the average R at the ceiling level was R10 after thermal bridging & gaps are factored in, and it's likely to be leaking considerable air, bypassing much of that insulation.

With 2-3" of 2lb foam gluing the roof deck to the rafters & top plate of the studwall you will have added a considerable amount of structural rigidity, and resilience to hurricane-force winds. With a vented attic there's a high upward pressure imparted to the roof decking by the aerodynamic forces of the wind. Air-sealing it reduces that by a lot, but one broken window and you're back in the same boat. But 2-3" of cc foam is at least as effective than a screwed-down roof deck at retaining the roof deck, and glued to the studwalls it's similar to framing ties. (If you need a further rationalization for spending the ~$2 per square foot of roof area for 2" of R6/inch foam or 3" of R5/inch foam.)

FYI, 3 photos.  Roof, Rafters, insulation in attic floor where you can also see some uninsulated duct work.

Not sure if that worked....

What is the heat loss through 2400 sf of uninsulated slab? My feet ache just thinking about it.

I would use as much insulated pad under carpet as you can stand, and the notion of jackhammering out the remaining hard surfaces so they can be insulated and re-poured might even be entertained.

I think Dana is on the right track with radiant overhead.

the foyer (stamped concrete).

That's interesting. Is that original? How much of that was done back in the 1950's? Was your home architect-designed?

Posted By ICFHybrid on 01 Sep 2011 10:23 AM
What is the heat loss through 2400 sf of uninsulated slab? My feet ache just thinking about it.

I would use as much insulated pad under carpet as you can stand, and the notion of jackhammering out the remaining hard surfaces so they can be insulated and re-poured might even be entertained.

I think Dana is on the right track with radiant overhead.

the foyer (stamped concrete).

That's interesting. Is that original? How much of that was done back in the 1950's? Was your home architect-designed?

Yes, the home was architect-designed and owned for 50 years. The stamped concrete appears to be original in the foyer. Probably won't be installing any carpets anywhere in the house--We hate them and we love dogs :-) Just some area rugs and some runners.

RE: Sealing and insulating the attic space and adding an ERV/HRV. Is it still possible to get a roofing warranty for a new roof if there is not the standard 3:1 sofit to ridge ventilation?

Ever tried to collect on a shingle warranty? ;-)

Yes, some shingle manufacturers have come around and won't automatically void the warranty for unvented insulated roofs or roofs with rafter-mounted radiant barrier. Soffit/ridge venting has a very modest effect on peak or average shingle temps- most of the cooling is exterior side radiation & convection even on the MOST ventilated roof. The combined R value of roof decking & felt underlayments are on the order of R1, not huge, but still significant, whereas the R value of the exterior air films are extremely low for roof pitches above 2:12 due to the turbulence of the induced convection, and the radiational cooling is at least half the equation at summertime peak temps. Soffit & ridge venting are more about setting up a modest convection loop for purging moisture from attics than they are about cooling the attic or roofing materials.

The color of the shingles has a far bigger effect on shingle-temps & lifespan, a of the solar reflectance and infra-red emissivity of the shingle itself. In any new roof in your climate it's worth picking something archtictecturally appropriate that's still a CRRC-listed or California Title 24-compliant product for high-slope roofs. (They're not all white...) See:

http://www.coolroofs.org/index.html

http://www.coolroofs.org/products/r...c_prod_id=

In general higher  the 3- year reflectance and emissivity numbers the better, but it's not super-critical, as long as the 3 year SRI (calculated from the reflectance & emissivity numbers, and listed in the far right column) is at least 25. 

Well, the original roof was probably close to bright white when new and is now a very light grey color. They are Cement/Asbestos composite shingles...

Just met with a roofer this morning to decide what our options are as far as roof repair or replacement and insulation of the roof or the attic floor instead. He was really big on adding lots of ventilation to the roof to make sure there was a warranty but I am less than convinced by that idea. What do people do with homes built air-tight with SIPs?

The roof is low to the ground and very visible so we have to make sure that whatever we do looks nice and is architecturally coordinated. Basically, a slate look or similar would work. Also, a metal roof would look very nice here too. Just not sure we can afford it...