Advice to fix/retrofit heating/cooling and insulation problems in 23 yr old house
I have a 2-story house in climate zone 3A (Tulsa Ok) with a lot of problems with heating/cooling due to poor insulation caused by poor quality construction and squirrel problems from the previous owner. I am trying to decide what are the most cost effective options (spray foam, blown insulation, reflective barrier, HVAC upgrades, ventilation) to fix my problems. What would you recommend my plan of attack should be? Below are more background details.
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Home: Built 1999, 4000 sq ft 2 story (1st story 2300 sq ft, 2nd story 1700 sq ft.); double-pane windows.
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Roof: Black asphalt shingle on plywood. Installed 2018. The roof is multi-geometry with 10 and 12 pitch. Estimated roof area is 5400 sq ft.
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HVAC Downstairs: 3 ton Goodman 16 seer 2-stage downstairs with 97% efficiency furnace. Installed 2020. Ducts installed in concrete slab
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HVAC Upstairs: 2.5 ton Trane installed 1999. (Working ok but it will probably die in the next few years.) Flexible foil ducts installed in attic. Blower door test indicates that ducts are leaking about 1 ton of conditioning.
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Insulation: Blown fiberglass insulation in attic is approx 6” – 10” deep due to settling and previous squirrel infestation. There are two large rooms with cathedral/vaulted ceilings with batt insulation between sheetrock ceiling and roof deck. Some of the 2nd story rooms have knee walls and full height walls facing into the attic. These rooms have exposed fiberglass batt insulation in many places that had been stripped by squirrels. I have replaced the major voids.
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Attic ventilation: Rectangular mesh soffit vents. Many of the vents and soffit eaves were filled with grasses, leaves and fiberglass insulation from squirrels. Six square roof vents installed near the ridge. Attic Temp runs about 20 deg hotter than ambient air temp in summer.
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Hot water tank – Gas 75 gal. installed 1999
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Electric Usage: 2600 KWH/mo avg ($3600/yr). Lowest months ~1200 KWH (spring/fall), Highest months 5300 KWH (summer)
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Gas Usage: 10 mcf/mo avg ($1300/yr). Highest 22 mcf/mo winter, 3 mcf/mo summer
Problems:
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Difficult to keep house temp in comfortable range. HVAC runs almost continuously upstairs in the summer and can’t get inside summer temps below 76 to 80 during the heat of the day. I have installed portable ac units in two of the upstairs rooms to help get temps down.
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Rooms have cold/hot spots due to poor/missing insulation (the poor quality insulation construction was not visible until I cut access panels into previously inaccessible areas of the attic). Temperatures between rooms upstairs vary by as much as 10-15 deg.
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Poor Attic ventilation due to squirrel nest material in soffits (most of it is difficult to access and remove).
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High Electric Utility cost (although the elec bills are high, the cost for upgrades being consider could take 10- 30 years to payout)
Possible solutions being Considered:
Insulation:
A) Install radiant barrier foil on roof rafters and knee walls. Install new R30+ blown insulation on the attic floor. Clean out soffit vents as much as possible (difficult to get enough access to clean out fully). Possibly replace soffit vents with continuous perforated soffits and add a few more roof vents.
Or B) Open cell spray foam on underside of attic roof and rafters. Must replace the upstairs HVAC (with gas furnace) and hot water tank with +95% efficiency units because they are located in the confined attic that will become unvented. Spray foam is more expensive but it eliminates the need to clean out the rodent trash from the soffit vents (very difficult) to improve attic ventilation. Spray foam can also help eliminate the need to add insulation to attic interior wall areas that are difficult to access . I like the spray foam option because I can have a floored, conditioned attic for storage, however I am concerned about risk of off-gassing if the contractor doesn’t mix the foam properly.
Upstairs HVAC ducts: Replace with new duct if using blow insulation. Is it still a good idea to replace if using spray foam even though the leaks will be contained in the conditioned attic?
Estimated Improvement Cost:
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Upstairs HVAC 99% efficient $16k
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New upstairs Flexible Ducts $7k
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Spray Foam $10k to $15k (includes removing old insulation on attic floor)
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Radiant Barrier Foil on rafters DIY $1500
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New R30+ Blown Insulation $6K.
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DIY Fix Attic soffit ventilation $1k
Thanks
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Replies
Addressing the heating and cooling issues in your Tulsa, OK home requires a multi-faceted approach, focusing on improving insulation, sealing ductwork, enhancing ventilation, and upgrading HVAC systems as necessary. Given the problems you've outlined and the solutions you're considering, here's a recommended plan of attack based on cost-effectiveness and overall impact on comfort and energy efficiency:
1. Ductwork First
Given the significant leakage indicated by your blower door test, prioritize sealing or replacing the upstairs HVAC ducts. Duct leakage not only wastes energy but also significantly impacts comfort. If you opt for spray foam insulation, replacing the ducts might still be beneficial to ensure they are properly insulated and sealed, even if they will be in a conditioned space.
2. Improve Attic Insulation and Ventilation
Before considering spray foam, address the attic's insulation and ventilation. Removing squirrel nest materials and ensuring soffit vents are clear are essential steps.
Adding a radiant barrier may offer some benefit in reducing heat gain, but the primary focus should be on adding sufficient insulation to the attic floor. R30+ blown insulation is a good choice and can be more cost-effective than spray foam.
Consider enhancing attic ventilation with additional roof vents or a ridge vent to help manage attic temperatures, especially if you're not going with spray foam.
3. Spray Foam vs. Blown Insulation
Evaluate the cost-benefit of spray foam carefully. While it offers excellent air sealing and insulation, the cost and potential issues with off-gassing or improper installation should be considered. If the HVAC and hot water tank are nearing the end of their lifespan, replacing them with high-efficiency units could be worthwhile, but factor these costs into your decision.
4. HVAC Upgrades
Given the age of your upstairs HVAC unit, planning for its replacement is wise. Consider a high-efficiency unit that matches the needs of your now better-insulated and sealed home. The new unit's size should be based on an updated load calculation after insulation and air sealing improvements.
5. Addressing Insulation Gaps
For areas with missing or damaged insulation, particularly around knee walls and cathedral ceilings, ensure these are properly insulated and air-sealed. This might involve replacing or adding batts and using rigid foam boards for additional insulation where possible.
Estimated Improvement Priorities
Short Term: Seal/replace ductwork, clear and improve attic ventilation, and add blown insulation to the attic floor. These steps will likely offer the most immediate improvements in comfort and energy efficiency.
Medium Term: Plan for HVAC upgrades, focusing on the upstairs unit and considering energy efficiency and the improved insulation of your home.
Long Term: If choosing spray foam, do so as part of a comprehensive plan that includes upgrading mechanicals in the attic to high-efficiency models.
Cost Considerations
Balancing the cost of upgrades with potential energy savings is crucial. While some improvements like duct sealing and adding blown insulation have quicker payback periods, others like spray foam and HVAC upgrades are more substantial investments that should be evaluated for their long-term benefits to your home's comfort and energy performance.
By prioritizing ductwork, improving attic insulation and ventilation, and carefully considering the benefits of spray foam versus its costs, you can create a more comfortable, energy-efficient home. Always consult with local energy efficiency professionals or contractors who can provide specific advice based on a detailed assessment of your home.