ENVELOPE NOTES · THERMAL ENVELOPE
Every weatherization measure, filed the same way.
Each measure is cut from the same section: the part of the envelope it covers, the R-value it targets, what the work costs, what it tends to save, whether you can do it yourself, and how long it lasts. Compare measures on one wall instead of trusting a sales sheet.
Cut the wall into layers
Attic & Roof
All Attic & Roof →
Attic & Roof
Why Your Attic Floor Is Where Heat Actually Escapes
R-valueTarget R-38 to R-60 in most climates, depending on local energy code and existing insulation
CostTypical installed cost ranges from $1,500 to $5,000 for blown-in insulation and air sealing, varying by attic size, existing conditions, and labor market
SavingsOften reduces heating and cooling demand by 10% to 20%, with larger effects when air sealing is included and the attic is leaky
AccessCareful homeowner can install batt or blown-in insulation and seal accessible leaks, but a professional crew is recommended for dense-pack, complex air sealing, or safety concerns
Heat does not respect the rooms we live in.
Attic & Roof
Rafter Vents and Baffles: Keeping Insulation From Blocking Airflow
R-valueBaffles themselves are not rated for R-value; they preserve the designed R-value of the adjacent insulation (often R-30 to R-60 in attics)
CostDIY materials: roughly $1 to $3 per baffle; installed by a crew: roughly $3 to $8 per baffle, or $200 to $800 for a typical attic depending on access and quantity
SavingsIndirect: helps maintain insulation R-value and reduce heat gain/loss; typical effect on heating and cooling demand is modest, often in the low single-digit percentage range when airflow was previously blocked
AccessCareful homeowner can install in an accessible attic; a crew is needed for tight spaces, low clearances, or when insulation must be moved
Rafter vents and baffles are small, inexpensive components that protect one of the most important conditions in an attic: unobstructed airflow from the soffit to the ridge.
Attic & Roof
Flat Roof Insulation and the Case for Rigid Foam Boards
R-valueRigid foam boards typically range from about R-4 to R-6.5 per inch of thickness depending on the foam type; flat roof targets commonly fall between R-20 and R-40, with colder climates pushing toward the higher end.
CostInstalled cost commonly falls in a broad band from roughly a few dollars to the low teens per square foot, driven by foam type, thickness, tear-off, and whether a new membrane is part of the job.
SavingsReduces conductive heat loss in winter and heat gain in summer through the roof plane; effect on total heating and cooling demand varies widely with climate, existing insulation, air sealing, and roof area.
AccessA crew is generally needed for membrane work, hot or adhesive application, and safe roof access; a careful homeowner may handle small repairs, inspection, and interior-side air sealing where accessible.
Heat does not respect the shape of a roof.
Attic & Roof
Radiant Barriers in Hot Climates: What They Do and Do Not Do
R-valueNot rated as an R-value; radiant barriers reduce radiant heat transfer and may add a small R-value (typically R-1 to R-2) depending on the product and installation.
CostInstalled cost typically ranges from $0.50 to $2.50 per square foot, depending on material, labor, and attic complexity; DIY materials often $0.20 to $1.00 per square foot.
SavingsIn hot climates, can reduce cooling demand by roughly 5% to 15% when properly installed and combined with air sealing and insulation; savings vary with climate, duct location, and existing insulation.
AccessA careful homeowner can install some radiant barrier products, but proper installation requires attention to safety, moisture control, and local codes; complex attics or roof-integrated products may need a crew.
In hot climates, the roof and attic are often the largest single source of unwanted heat gain in a home.
Attic & Roof
Blown-In Attic Insulation and How Settling Changes R-Value
R-valueR-30 to R-60 installed; settled thickness often reduces effective R-value by 10–20% over time
Cost$1.50–$3.50 per square foot installed, depending on material, thickness, and local labor rates
SavingsTypically reduces heating and cooling demand by 10–20% when added to an under-insulated attic, but actual savings vary with climate, existing insulation, and air sealing
AccessCrew recommended for blown-in insulation; a careful homeowner can handle prep work, air sealing, and small touch-ups
Blown-in attic insulation is one of the most practical upgrades for an under-insulated home because it targets the largest uncontrolled heat loss path in many buildings: the ceiling plane.
Attic & Roof
Roof Deck Insulation for Vaulted Ceilings Without an Attic
R-valueTarget R-value varies by climate: R-20 to R-30 in mild zones, R-30 to R-40 in moderate zones, R-40 to R-60 in cold zones; always follow local code.
CostTypical installed cost ranges from $4 to $12 per square foot for interior retrofit, and $8 to $20 per square foot for exterior retrofit, depending on material, access, and labor.
SavingsCan reduce heating and cooling demand by roughly 10% to 30% when addressing a previously under-insulated roof deck, but actual results depend on air sealing, climate, and existing conditions.
AccessInterior retrofit is often a careful homeowner project for open rafter bays, but exterior retrofit and complex assemblies require a crew.
Vaulted ceilings without an attic are a common feature in modern homes, but they create a thermal weak point.
Attic & Roof
Sealing Attic Hatch Doors and Pull-Down Stairs Properly
R-valueTarget R-10 to R-25 for the insulated cover or hatch, depending on climate and existing attic insulation level
CostDIY materials $50–$200; professional installation $300–$1,200 depending on assembly complexity and labor
SavingsTypically reduces heating and cooling demand by 5–15% when the attic access is a major leakage point, though actual savings vary with climate, home tightness, and existing insulation
AccessCareful homeowner can often do a basic weatherstrip and insulation cover; a crew is recommended for pull-down stairs with structural or fit issues, or when air sealing requires two people
Attic hatch doors and pull-down stairs are among the most overlooked openings in a home's thermal envelope.
Attic & Roof
Knee Walls, Dormers, and the Attics That Never Get Sealed
R-valueTarget R-15 to R-21 in 2x4 and 2x6 knee wall and dormer cavities when space allows; R-13 to R-15 in shallow or obstructed bays; rigid or closed-cell options can reach R-10 to R-21 per inch depending on material.
CostTypical installed cost ranges from roughly $1,200 to $6,500 depending on attic size, number of dormers, access difficulty, and whether air sealing, baffles, and ventilation corrections are included.
SavingsCommonly reduces heating and cooling demand by a modest to moderate range, often in the low single digits to mid-teens percentage range for the whole house, with larger effects when the attic perimeter was previously open and leaky.
AccessA careful homeowner can handle small access-panel sealing and simple insulation repairs, but full knee wall and dormer work usually requires a crew because of tight spaces, fall hazards, and the need for continuous air and thermal barriers.
Knee walls and dormers are the awkward edges of an attic, and that awkwardness is exactly why they are so often left unsealed.
Walls
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Walls
Cavity Insulation in Framed Walls: Batts, Blown, and Dense-Pack
R-valueR-13 to R-15 for 2x4 walls; R-19 to R-21 for 2x6 walls; dense-pack and blown-in can achieve similar or slightly higher values depending on density and cavity depth. Target R-value should match climate and code, often R-20+ for cold climates.
CostTypical installed cost ranges from about $1.50 to $4.50 per square foot of wall area, depending on material, cavity depth, access, and labor. Dense-pack and blown-in tend to be at the higher end; batts at the lower end for simple, open cavities.
SavingsHeating and cooling demand can drop by roughly 10% to 30% when upgrading an uninsulated or poorly insulated wall, but actual savings depend on climate, air sealing, existing insulation, and house tightness. Savings are often modest if air leakage and other envelope gaps remain.
AccessBatts in open cavities are a careful DIY possibility; blown-in and dense-pack almost always require a crew and specialized equipment. Retrofits into closed cavities are best left to professionals.
Cavity insulation in framed walls is one of the most direct ways to slow heat movement through the largest above-grade surface of many homes.
Walls
Continuous Exterior Insulation and the Thermal Bridge Problem
R-valueR-5 to R-20 continuous, depending on climate zone and wall assembly
Cost$2 to $6 per square foot installed for rigid foam or mineral wool, plus detailing
SavingsTypically 10 to 25 percent of wall-related heating and cooling demand, with diminishing returns at higher R-values
AccessCrew needed for most installations; a careful homeowner can handle small retrofits or detailing with proper guidance
Heat does not respect the tidy lines we draw on building plans.
Walls
Insulating Solid Masonry Walls Without Trapping Moisture
R-valueR-5 to R-15 for most residential retrofits; continuous rigid or mineral insulation in the R-5 to R-10 range is common, while thicker interior furring with batt or blown fill can reach R-13 to R-15 where space and drying allow
CostRoughly $3 to $12 per square foot installed for interior furring and insulation, and $8 to $25 per square foot for exterior rigid insulation with new cladding and trim; whole-wall projects commonly land in the low thousands to low tens of thousands depending on size, access, and finish work
SavingsTypically a modest reduction in heating demand, often in the range of 5 to 20 percent of wall-related losses, with smaller cooling effects; results depend heavily on air sealing, window and roof conditions, and how much of the wall was previously uninsulated
AccessA careful homeowner can handle small interior jobs such as sealing penetrations, installing rigid board on a furred wall, or adding a vapor-permeable insulation layer, but exterior retrofits, structural furring, flashing, and any work involving masonry repair or drainage details generally call for an experienced crew
Solid masonry walls are common in older homes, and they behave very differently from modern framed walls.
Walls
Rim Joists and Sill Plates: The Overlooked Band of Loss
R-valueR-10 to R-20 in most climate zones, with colder zones targeting the upper end of that range when rigid foam or closed-cell foam is used
CostRoughly a few hundred to a couple thousand dollars for a typical basement or crawlspace perimeter, depending on length, access, and material choice
SavingsOften a modest but noticeable reduction in heating demand, with smaller cooling effects in humid climates; results vary widely with existing leakage and climate
AccessA careful homeowner can handle exposed, dry, accessible rim areas with rigid foam and sealant; a crew is needed for closed-cell spray foam, tight crawlspaces, or any area with moisture problems
Most insulation conversations start at the attic and stop at the basement stairs.
Walls
Rigid Foam Sheathing and How Thickness Maps to R-Value
R-valueR-3 to R-10 per inch of rigid foam; common thicknesses yield R-5 to R-20 for the continuous layer
CostRoughly $1.50 to $4.50 per square foot installed, depending on thickness, substrate prep, and trim details
SavingsTypically reduces wall-related heating and cooling demand by about 5 to 20 percent when added to an uninsulated or under-insulated wall
AccessBest installed by a crew during siding replacement or new construction; a careful homeowner can handle small repairs or one-room retrofits with guidance
Rigid foam sheathing is one of the few wall upgrades that addresses two problems at once: it adds a continuous layer of insulation and it reduces thermal bridging through the studs.
Walls
Basement Wall Insulation From the Interior Side
R-valueR-10 to R-15 for continuous rigid foam or closed-cell spray foam; R-13 to R-21 for framed cavity insulation when combined with a continuous layer
CostInstalled cost typically ranges from about $1.50 to $4.50 per square foot, depending on material and site conditions; a typical 1,000-square-foot basement wall area might fall between $1,500 and $4,500
SavingsCan reduce total home heating demand by roughly 5 to 15 percent in homes with uninsulated basements, with cooling savings in some climates; actual results depend on climate, air sealing, and existing conditions
AccessA careful homeowner can install rigid foam boards and seal edges, but framed cavity insulation and spray foam usually require a crew for safety and code compliance
Basement walls are often the largest uninsulated surface in a house, and they sit in a uniquely harsh environment.
Walls
Framing Penetrations and What Thermal Bridging Really Costs
R-valueR-3.5 to R-6 per inch for continuous insulation; R-13 to R-21 for cavity insulation
Cost$1,500 to $7,000 for a typical whole-house retrofit, depending on accessibility and extent
SavingsTypically 5% to 15% reduction in heating and cooling demand when combined with air sealing
AccessCrew recommended for comprehensive work; careful homeowner can address exposed penetrations in basements or attics
Framing penetrations are the unglamorous details that quietly undermine an otherwise well-insulated wall.
Walls
Closed-Cell Versus Open-Cell Spray Foam in Wall Cavities
R-valueClosed-cell: R-6 to R-7 per inch; open-cell: R-3.5 to R-4.5 per inch. Target wall assembly R-value depends on climate and code, often R-13 to R-21 for 2x4 and 2x6 walls, with higher targets in cold climates.
CostInstalled cost typically ranges from $1.50 to $3.50 per square foot for open-cell and $2.50 to $5.50 per square foot for closed-cell, varying with thickness, access, and region.
SavingsHeating and cooling demand may be reduced by roughly 10 to 25 percent compared with uninsulated or poorly sealed walls, depending on climate, existing conditions, and air sealing details.
AccessCrew needed for spray application; careful homeowner can handle preparation and minor air sealing but not the spray foam itself.
Spray foam in wall cavities addresses two of the biggest drivers of heat loss and gain at once: missing insulation and air leakage.
Windows & Doors
All Windows & Doors →
Windows & Doors
Window Films and Storm Panels for Aging Single-Pane Glass
R-valueAdds roughly R-0.5 to R-2 depending on film type, number of layers, and air gap; storm panels create an additional dead air space that can raise the assembly toward R-2 to R-3
CostDIY film kits typically range from a few dollars to a few tens of dollars per window; professional film installation often runs in the range of several dollars to roughly twenty dollars per square foot; storm panels commonly range from roughly fifty to several hundred dollars per window installed, with DIY options at the lower end
SavingsTypically reduces heating and cooling demand through the glazing by a modest percentage, often in the range of a few percent to around fifteen percent of total window-related load, with the largest effects on the coldest or sunniest exposures
AccessCareful homeowners can install interior films and some exterior films; storm panels range from DIY-friendly kits to jobs best handled by a crew, especially on upper floors or with custom sizing
Single-pane windows are a known weak point in the building envelope.
Windows & Doors
Air Sealing Around Windows Without Cracking the Frame
R-valueAir sealing itself has no rated R-value; it preserves the assembly's intended insulation. The surrounding wall cavity is typically R-13 to R-21, and the window unit itself is commonly R-2 to R-5 depending on glazing and frame type.
CostRoughly $5 to $25 per linear foot of window perimeter for targeted sealing, or about $150 to $600 per window when a crew removes and reinstalls trim; whole-home window air sealing commonly falls in the $500 to $2,500 range.
SavingsAir sealing around windows typically reduces heating and cooling demand by a modest few percent to low double digits in leaky homes, with the largest effects where the rough opening is open to the wall cavity or exterior.
AccessA careful homeowner can seal accessible interior gaps with caulk, sealant, and backer rod; removing and reinstalling trim, addressing exterior gaps, or sealing behind finished surfaces generally calls for a crew.
Air sealing around windows is one of the least glamorous envelope measures, and that is exactly why it earns its place.
Windows & Doors
Door Sweeps, Thresholds, and the Bottom-of-the-Door Draft
R-valueNot rated as an insulation R-value; air-sealing measure. Target is a continuous, gasketed seal; no R-value applies to sweeps or thresholds themselves
CostDIY materials roughly $15–$60 per door; professional installation roughly $75–$250 per door depending on door type, threshold condition, and labor rates
SavingsTypically modest for heating and cooling demand; commonly reported in the low single-digit percentage range of total home energy use when combined with other air-sealing work, with wider variation depending on climate, door condition, and existing leakage
AccessCareful homeowner can do most sweeps and many threshold replacements; a crew is advisable for door bottom replacement, sill repair, or when the door frame or subfloor is damaged
The bottom of an exterior door is one of the most overlooked spots in a home's air barrier.
Windows & Doors
Why Window Replacement Rarely Pays Back on Energy Alone
R-valueR-2 to R-5 for typical replacement windows; R-3 to R-5 for high-performance units
Cost$300 to $1,200 per window installed; $500 to $2,500 per door installed
Savings5% to 15% of annual heating and cooling energy use, often less if air sealing and insulation are already addressed
AccessCrew needed for replacement; careful homeowner can do air sealing and weatherstripping
Window replacement is often sold as a straightforward energy fix, but the payback rarely comes from energy savings alone.
Windows & Doors
Replacing Glazing Units Instead of Entire Window Frames
R-valueTypically R-2 to R-5 for common double-pane units with low-e coatings and gas fills; triple-pane or high-performance units can reach R-5 to R-8. The existing frame and sash add little insulating value and may reduce overall assembly performance.
CostInstalled cost often ranges from roughly $200 to $900 per window for replacement glazing units, depending on size, glazing type, frame condition, and local labor. Full window replacement typically costs more, often $500 to $1,500 or more per window.
SavingsModest reductions in heating and cooling demand, often in the range of 5 to 15 percent of window-related energy use, with larger effects in older, single-pane windows and smaller effects where frames or air sealing remain poor. Savings vary with climate, window area, and existing performance.
AccessA careful homeowner can replace some glazing units in operable wood or vinyl sashes if the unit is removable and the frame is sound, but most projects require a crew for measuring, ordering, and safe installation, especially for fixed or large units.
Windows are often blamed for high energy bills, but the frame and the glass play different roles.
Windows & Doors
Weatherstripping Doors So It Survives a Full Season
R-valueNot rated as R-value; weatherstripping reduces air leakage. Target assembly performance is an airtight door with U-factor around 0.20–0.30 for the full door.
CostDIY materials: $15–$60 per door; professional installation: $100–$300 per door depending on door type and labor.
SavingsTypically reduces heating and cooling demand by 5–15% when sealing major door leaks, but actual savings vary with climate, existing leakage, and other envelope conditions.
AccessCareful homeowner can do it with basic tools; complex doors or damaged frames may need a crew.
Doors are the most-used openings in a house, and every trip through them flexes the seal that keeps outside air outside.
Windows & Doors
Sash Locks, Latches, and Tightening a Loose Double-Hung Window
R-valueNo meaningful R-value of its own; the measure preserves the assembly's existing center-of-glass value (roughly R-1 for single glazing, R-2 to R-3 for common double glazing, higher with low-e or added glazing panels) by restoring the designed air barrier rather than adding insulation
CostRoughly $15 to $60 in parts for a homeowner replacing locks, latches, and weatherstripping on a few windows; roughly $150 to $400 per window for a carpenter or window technician to repair sashes, replace hardware, adjust stops, and re-weatherstrip, with higher bands where sash repair or partial rebuild is needed
SavingsModest but real: tightening locks and latches and restoring perimeter seals typically trims a small single-digit to low-double-digit percentage of heating demand in rooms dominated by leaky windows, with cooling-season gains where infiltration and solar gain are both managed; results depend on how leaky the window was and how much other envelope work is done
AccessCareful homeowner for lock, latch, and weatherstrip replacement and for minor sash adjustment; a crew for sash repair, glazing work, rot, out-of-square frames, or any window that will not operate safely
Double-hung windows are the most common operable window in older housing, and they are also one of the most forgiving places to start envelope work.
Air Sealing
All Air Sealing →
Air Sealing
The Stack Effect and Why Cold Air Enters Low and Leaves High
R-valueAir sealing itself has no R-value; it preserves the rated R-value of adjacent insulation. Target assemblies typically range from R-13 to R-60 depending on climate and location.
CostDIY air sealing materials typically run $50–$300; professional air sealing often ranges from $500–$2,500 depending on home size, accessibility, and climate zone.
SavingsHeating and cooling demand commonly drops by 5–20% when major air leaks are sealed, with the largest reductions in leaky, older homes.
AccessCareful homeowners can seal accessible leaks in attics, basements, and rim joists; a crew is recommended for combustion safety, blower-door testing, and hard-to-reach areas.
Air sealing earns its place because it addresses the driving force behind some of the most persistent comfort complaints in homes: the stack effect.
Air Sealing
Chasing Drafts With a Smoke Pencil Before You Insulate
R-valueAir sealing itself has no R-value; it preserves the rated R-value of adjacent insulation (e.g., R-13 to R-60) by stopping air movement.
CostDIY: $50–$200 in materials; professional: $300–$1,500 depending on home size and complexity.
SavingsTypically reduces heating and cooling demand by 5–15% when combined with existing insulation, with diminishing returns in already tight homes.
AccessCareful homeowners can seal accessible areas like attics and basements; a crew is recommended for hard-to-reach or combustion-safety-related zones.
Air sealing is often the most cost-effective step you can take before adding insulation.
Air Sealing
Top Plates, Plumbing Penetrations, and Hidden Air Leaks
R-valueNo intrinsic R-value; air sealing is a leakage-control measure. Where insulation is added or restored at the same location, common targets are R-13 to R-21 in 2x4 and 2x6 cavities, R-30 to R-49 in attics, and R-19 to R-30 at rim and band areas, depending on climate zone
CostRoughly $500 to $3,500 for a targeted air-sealing and insulation-repair scope in a typical single-family home; whole-house air sealing with attic and rim work commonly runs $1,500 to $6,000, with higher bands in complex or older homes
SavingsTypically a modest reduction in heating and cooling demand, often in the range of 5 to 15 percent of space-conditioning energy when combined with insulation repair, with larger effects in leaky older homes and smaller effects in already tight ones
AccessPartly do-it-yourself: exposed attic top plates, open rim areas, and accessible penetrations can be sealed by a careful homeowner; concealed chases, finished-wall penetrations, combustion zones, and insulation work generally call for a crew
Most homes do not lose heat through a single dramatic hole.
Air Sealing
Recessed Light Covers and the Holes Above Your Ceiling
R-valueCovers add little intrinsic R-value; the assembly target is R-30 to R-60 in cold climates, depending on climate zone and existing insulation depth. Covers protect insulation contact and reduce convective bypass but do not replace missing insulation.
CostRoughly $15 to $60 per fixture for basic materials if self-installed; $75 to $250 per fixture for professional installation, depending on access, fixture type, and whether insulation work is bundled.
SavingsTypically modest on their own, often in the low single-digit percentage range of total heating and cooling demand; larger when many fixtures are open to an unconditioned attic and are combined with attic air sealing and insulation improvements.
AccessA careful homeowner can install simple covers on accessible fixtures from below or above in an open attic; a crew is recommended for IC-rated versus non-IC-rated confusion, tight clearances, wiring, and any work near knob-and-tube or damaged wiring.
Recessed light covers are not glamorous.
Air Sealing
Sealing Chimney and Flue Chases Without Blocking Clearances
R-valueR-13 to R-21 for chase wall and attic-floor assemblies, with rigid mineral wool or fiberglass batts rated for the assembly; clearances to the flue remain the governing limit, not the R-value.
CostRoughly $400 to $2,500 installed depending on chase length, access, whether the flue must be re-flashed or re-clearanced, and whether interior trim or drywall must be opened and repaired.
SavingsTypically a modest but persistent reduction in winter heat loss and summer heat gain, often in the low single digits to low teens as a percentage of whole-house envelope losses, largest when the chase was previously wide open to the attic.
AccessA careful homeowner can seal and insulate an accessible attic-side chase with proper clearances and fire-rated materials; interior chases, masonry rebuilds, and any work near the flue collar or roof penetration are crew work.
A chimney chase is one of the few places in a house where a large hole in the thermal envelope is also a code-regulated clearance zone.
Air Sealing
Duct Sealing Inside the Envelope Before Adding Insulation
R-valueDuct insulation typically rated R-6 to R-12; sealing itself has no R-value but enhances insulation performance
CostTypical installed cost ranges from $500 to $2,500 depending on accessibility and extent of sealing
SavingsCan reduce heating and cooling demand by roughly 10% to 30% when ducts are inside the envelope and leaks are significant
AccessCareful homeowner can seal accessible ducts with mastic and mesh; a crew is needed for concealed or hard-to-reach runs
Duct sealing inside the envelope often gets overlooked because it is not as visible as adding insulation to an attic floor or swapping out a furnace filter.
Air Sealing
Planning a Blower Door Test Around Your Weatherization Work
R-valueNot an R-value measure; blower door testing is a diagnostic. It quantifies leakage in CFM50 and, when paired with air sealing, supports the integrity of the insulation R-value already installed (commonly R-30 to R-60 in attics, R-13 to R-21 in walls)
CostDiagnostic-only blower door test typically $250 to $600; a test-in and test-out pair for a retrofit project commonly $400 to $1,000; air sealing work itself often $500 to $3,000 depending on attic, rim joist, and penetration count
SavingsAir sealing guided by blower door results commonly reduces heating and cooling demand by roughly 5 to 20 percent, with the larger end of the range in leaky older homes and the smaller end in already-tight newer construction
AccessBlower door testing requires a trained operator and calibrated equipment; a careful homeowner can do the prep work and much of the accessible air sealing, but a crew is needed for combustion safety testing, dense-pack work, and any sealing near flues or gas appliances
A blower door test is not weatherization work in itself.