Insulation in a wall or a joist bay absorbs sound. It does not block it. That one distinction decides whether a soundproofing job satisfies or disappoints.
The published figures show how far apart the two halves are. Filling an empty cavity is worth roughly 4 to 11 points of Sound Transmission Class in the guideline table and technical report quoted below. Changing how the wall is built is worth more. In PABCO Gypsum’s current tests, a 2x4 wall with fiberglass batts and one layer of 5/8-inch Type X each side rates STC 35; resilient channel on one side takes it to 48, and a second row of studs to 56. We install the absorption half: mineral wool and fiberglass batts, dense-pack cellulose, blown-in fiberglass and open cell spray foam. Resilient channel, double drywall and mass-loaded vinyl are drywall and framing work, described below.
What insulation can and cannot do for noise
PABCO’s Sound Design Guide separates absorption, where sound energy is converted into very tiny amounts of heat inside a material, from transmission, the transfer of energy from one side of a partition to the other. Insulation is an absorber: it damps the resonance of the air space between two sheets of drywall. What stops sound getting through is the weight of those sheets and whether the vibration has a rigid path from one to the other.
The second split is between airborne noise — speech, television, music — and structure-borne noise, which PABCO defines as “any noise source whose primary radiation comes from impact (footsteps on an upstairs floor, for example) or vibration of solid structures.” Its glossary adds that impact noise “transmits through partitions via framing and other rigid connections.” Cavity insulation raises the ratings for both kinds, but for footsteps the covering on the floor above can move the number far more, as the floor section below shows. And insulation does nothing for a gap: a hole in a partition is the loudest thing in it.
STC and IIC: how sound ratings are measured
Sound Transmission Class is a single number for airborne sound. PABCO describes the method: transmission loss is measured in a laboratory from 125 Hz to 4,000 Hz, a contour is fitted to it under ASTM Classification E413, and the rating is read at 500 Hz; the laboratory test behind it is ASTM E90. PABCO adds that STC “very roughly reflects the decibel reduction in noise that a partition can provide.” Impact noise gets its own number, Impact Insulation Class, measured with a tapping machine on the floor above under ASTM E492. A floor can have a good STC and a poor IIC at once, which a homeowner hears as “I can’t make out the words, but I hear every step.”
The Technical Services Information Bureau’s current bulletin on metal-framed walls, dated June 2025, carries a plain-language table of what each rating sounds like through a wall:
- STC 25: normal speech can be understood easily and heard distinctly.
- STC 30: loud speech can be understood well; normal speech heard but not understood.
- STC 35: loud speech noticeable but not understood.
- STC 40: the beginning of privacy.
- STC 42: loud speech heard as a murmur.
- STC 45: loud speech not noticeable.
- STC 50: very loud sounds such as musical instruments or a stereo can be faintly heard.
- STC 60 and above: most sounds impossible to hear.
Check the evidence behind any rating before you rely on it. PABCO notes that under the International Code Council’s G2-2010 acoustics guideline a test report older than 20 years does not provide adequate validation for a design, that a wall rated STC 51 in 1968 “would not achieve an STC rating above 46” if tested today, and that such assemblies “are still presented in current industry handbooks.” A recent publication date therefore proves nothing about when a wall was tested, and the figures quoted below are not equally strong. PABCO’s and ROCKWOOL’s walls carry test report numbers but no test dates. The American Wood Council’s floors carry test numbers from a series run in 2017. BASF’s ratings carry only UL design numbers, with no laboratory, report number or test date; the TSIB table is a guideline, not a test; and the Cellulose Insulation Manufacturers Association’s figure comes from an undated web page. When a quote or a product sheet names an STC, ask for the laboratory, the report number and the test date, and give less weight to any number that comes without them.
What each change to a wall is worth
PABCO’s 2025 Sound Design Guide lists wood-stud walls tested by an independent laboratory, each with its report number, and every one of these has the same 3 1/2-inch R-13 fiberglass batts in the cavity. Compare each line with the first:
- STC 35 — 2x4 studs 16 inches on center, one layer of 5/8-inch Type X each side.
- STC 38 — the same wall with two layers each side.
- STC 41 — one layer each side, studs 24 inches on center.
- STC 48 — one layer each side, 16-inch studs, resilient channel on one side.
- STC 56 — two separate rows of 2x4 studs with a 1-inch gap, batts in both rows, one layer each side.
Doubling the board bought 3 points. Spreading the studs bought 6. The channel bought 13, and the second row of studs, with its own batts, bought 21. The batts were in every wall, so the insulation is not what separates 35 from 56 — the framing is. Everything below about materials sits inside that frame.
PABCO’s list cannot show what the batts themselves are worth, because they are in every wall. The Technical Services Information Bureau’s guideline table for metal-stud walls separates them: with 3 5/8-inch studs 24 inches on center and one layer of 5/8-inch Type X each side, it puts the wall at STC 35 to 39 with an empty cavity and 45 to 50 with fiberglass batts, and across its rows the batts raise the range by 4 to 11 points. TSIB says its ranges are “for guide purposes only,” so read them as a guideline, not a test result.
Mineral wool versus fiberglass batts for sound
ROCKWOOL’s current Safe’n’Sound data sheet, issued November 2025, lists the stone wool batt at a nominal 2.5 lb/ft³ with a Noise Reduction Coefficient of 1.10 at 3 inches and 1.25 at 6 inches under ASTM C423. That sheet carries no wall ratings. ROCKWOOL’s tested walls are in a separate document, its Acoustic Wall Assemblies Catalog, issued August 2026. For 2x6 studs 16 inches on center with 5/8-inch Type X each side, the catalog lists STC 36 with 3 inches of Safe’n’Sound, STC 38 with 5.5 inches of ROCKWOOL stone wool, and STC 53 with the 5.5 inches plus resilient channel. A 2x4 wall with 3 inches of Safe’n’Sound, 5/8-inch board and resilient channel is listed at STC 51.
Set those beside PABCO’s fiberglass walls — 35 plain, 48 with channel — and stone wool reads a few points higher. Do not read much into it. The two sets come from different laboratories and different channel products; the American Wood Council notes that results from different laboratories “are often not comparable,” and PABCO that the choice of resilient channel “can result in drastically different” results. Within each manufacturer’s own list the pattern matches: in ROCKWOOL’s 2x6 wall, going from 3 inches of stone wool to 5.5 bought 2 points and adding the channel bought 15. TSIB puts it in general terms: “Batt insulation thickness provides better sound control than batt insulation density,” and the batt “must fit without gaps.”
Noncombustibility does not separate them either. ROCKWOOL lists Safe’n’Sound as noncombustible under ASTM E136, with a flame spread index of 0 and a smoke developed index of 0 under ASTM E84. Owens Corning’s data sheet classifies its unfaced EcoTouch fiberglass batt as noncombustible under the same E136 test, and lists it at 25 and 50 under E84. Owens Corning’s fire warning is about facings: kraft and standard foil facings “will burn and cannot be left exposed.” ROCKWOOL also calls its batt water and moisture repellent and an easy friction fit for wall, ceiling and floor applications. For a sound wall, choose an unfaced batt of either fiber on fit, handling and price, and cut it to fill the cavity. If the budget is limited, it moves the number more when it goes to the framing.
Open cell versus closed cell spray foam for sound
These two are not equals, and closed cell sold as a sound product is the wrong product. BASF publishes absorption coefficients for both under ASTM C423: open cell at 3.5 inches has an NRC of 0.65, peaking at 0.88 at 500 Hz and falling to 0.22 at 125 Hz; closed cell at 2 inches has an NRC of 0.10. Open cell is soft and open-structured, so it absorbs in the mid and high frequencies. Closed cell is rigid and absorbs very little.
BASF’s 2024 tech tip on sound lists these assemblies with its open cell foam under a heading that calls them tested. It identifies each by UL design number and gives no laboratory, report number or test date:
- STC 34 — interior partition, 2x4 studs 16 inches on center, one layer of 5/8-inch Type X each side, 3.5 inches of open cell (UL U305).
- STC 33 and 34 — exterior walls with OSB sheathing and 5/8-inch gypsum: 2x4 studs with 3.5 inches of open cell, then 2x6 studs with 5.5 inches.
- STC 57 — a double 2x4 partition with two layers of 5/8-inch Type X each side, a 1-inch air space, and 3.5 inches of open cell in one row of studs; the other row has no insulation.
The 34 sits within a point of PABCO’s 35 for the same wall with fiberglass, though without a report behind BASF’s number the two cannot be checked side by side. Two more inches of foam in a deeper exterior wall bought one point. The jump to 57 is not the foam: that assembly split the framing into two rows and doubled the board on both faces at the same time, with only one row insulated. For closed cell, the tech tip gives no tested wall rating: its two closed cell rows are footnoted as “typical STC values,” so they are not quoted here as test results. BASF does argue that closed cell’s rigidity “inhibits structural-borne sound transmission”; that is the manufacturer’s position, and it sits beside a measured absorption coefficient of 0.10.
Open cell earns its place where a batt cannot fill cleanly: a bay crowded with wiring and pipes, a knee wall, a floor of open-web trusses. BASF lists an 18-inch truss floor with 3.5 inches of open cell, resilient channel, 5/8-inch gypsum and a click-lock floor over an acoustical pad at STC 57 and IIC 50, and describes its foams as air barrier materials under ASTM E2178 and E283. One rule travels with foam: the residential code requires foam plastic to be separated from the interior by a thermal barrier such as 1/2-inch gypsum wallboard (R316.4 of the 2021 IRC in Connecticut, R303.4 of the 2024 IRC in New Jersey and New York). See open cell versus closed cell.
Dense-pack for walls and ceilings already closed
Everything above assumes an open cavity. Dense-pack is for the wall nobody wants to strip: cellulose or fiberglass blown through small holes at high density until the cavity is firm, then the holes are patched. It flows around wiring and pipes where a batt would have been cut and compressed. It is one of two ways we fill a finished wall without taking the board off; injection foam, pumped through similar holes, is the other, and no sound rating quoted here covers it, so ask for its tested assembly as you would for any product.
Set the expectation by the framing. Dense-pack fills the cavity; it adds no board and breaks no rigid path, so a dense-packed single-stud wall is still a single-stud wall, and PABCO’s filled 2x4 walls with ordinary Type X rate 35 to 45 depending on stud spacing and layers of board. The Cellulose Insulation Manufacturers Association says cellulose “may be used to achieve STC ratings as high as 70 depending on the wall or partition assembly,” with absorption “upwards of .80 or higher.” The qualifier is the point: 70 describes an elaborate assembly, not a material. If a closed wall has to reach 45 or better, dense-pack is the first half and drywall work is usually the second, covered below. See wall insulation and insulation for older homes.
Party walls and what code requires
Apartment and condominium buildings that come under the building code are covered by Section 1206 of the International Building Code: the 2024 edition as adopted in New Jersey, New York’s 2025 Building Code, and the 2021 edition in the 2022 Connecticut State Building Code. All three require walls, partitions and floor-ceiling assemblies between dwelling units to reach STC 50 tested to ASTM E90, or a Normalized Noise Isolation Class of 45 if field tested to ASTM E336, and floor-ceilings to reach an Impact Insulation Class of 50 under ASTM E492, or a Normalized Impact Sound Rating of 45 if field tested. The airborne section, 1206.2, also requires penetrations for piping, electrical devices and ducts to be sealed, lined, insulated or otherwise treated to keep the rating.
Townhouses and two-family houses come under the residential code, and there the answer depends on the state. Connecticut’s 2022 State Building Code adopts Appendix AK, Sound Transmission, of the 2021 IRC, and New Jersey’s one- and two-family dwelling subcode adopts the 2024 edition of the same appendix, re-lettered Appendix BG. Both require walls and floor-ceilings separating dwelling units, including adjacent townhouse units, to reach STC 45 (or NNIC 42 in the field), and floor-ceilings between units to reach IIC 45 (or NISR 42). Their airborne sections, AK102.1 and BG102.1, carry the same penetration rule as the building code. New York’s 2025 Residential Code prints that appendix for information only, so none of it is a requirement there. These sections cover what separates one dwelling unit from another or from common areas and set nothing for the walls inside a single home; how they apply to work on an existing wall is the building official’s call.
In a condominium or a co-op, the association normally owns the assemblies between units and decides what may be changed. Before any work starts, ask the board or managing agent in writing what approval is needed, and give them the specific assembly you plan to build — the tested design, its report number and its STC — so they are approving something they can check.
For new construction the step is the same in all three states: choose a tested assembly that meets the number — STC 50 and IIC 50 under the building code, STC 45 and IIC 45 under the Connecticut and New Jersey residential appendix — and show it on the permit drawings with its report number. Under the building code, Section 1206 also accepts an engineering analysis that compares the design with tested assemblies. Then build it as tested, because the insulation type and thickness are part of the rating. We install the insulation and air sealing in new townhouses, two-families and apartment buildings to the assembly on the drawings; the framing, channel and board belong to the builder’s other trades.
Floors over garages, basement ceilings and footsteps
A floor is two problems. The airborne half responds to cavity insulation. The American Wood Council’s 2019 technical report on wood-framed floors says the presence of insulation “always results in an increase in STC and IIC values,” and puts the airborne gain at 7 to 11 STC points for floors without a concrete topping, which is how most house floors are built, and 4 to 7 for floors with a gypsum-concrete topping. The Council’s own test series, run at the National Research Council of Canada in 2017, shows the topped case: in four matched pairs, taking the batts out cost 4 to 6 STC points. The report’s general figures also draw on earlier National Research Council test series published in 2000 and 2005.
One condition sits under all of those numbers: every floor in the report’s database had a drywall ceiling hung on resilient channel, and the Council describes the batts’ benefit as absorption within the cavity formed between the floor, the ceiling and the framing. An open-joist basement ceiling has no such cavity, and no figure quoted here describes it. If yours is open, fill the bays and then close them with drywall, on resilient channel if you can; the Council calls resilient channels “typically necessary” for a floor to reach the minimum ratings the code sets between dwelling units. We fill the bays; the ceiling is drywall work.
A room over an attached garage usually starts with its ceiling closed, because the residential code requires one under living space: 5/8-inch Type X gypsum board in Connecticut and New York, and a one-hour fire-rated floor-ceiling in New Jersey. We can dense-pack those bays through the garage ceiling and patch the holes, and the code requires anything that penetrates that ceiling to be protected so it keeps working as a fire separation. See garage insulation for each state’s details.
The impact half — footsteps, dropped objects — depends more on what is walked on. The Council’s report says IIC ratings “can be greatly affected by the type and characteristics of floor coverings,” and its measurements show how much. One floor — 9.5-inch I-joists 24 inches on center, a 23/32-inch OSB subfloor, 6-inch fiberglass batts, resilient channel and one layer of 5/8-inch gypsum board — was tested under five coverings:
- IIC 44 with cushioned vinyl.
- IIC 46 with click laminate.
- IIC 48 with ceramic tile.
- IIC 64 with thin carpet and pad.
- IIC 70 with thick carpet and pad.
Same framing, same batts, same ceiling: the covering moved impact performance by 26 points. Batts count for footsteps too: on two gypsum-topped floors in the same series, taking them out cost 6 and 2 IIC points. Those were different floors from the one above, so the figures are not a strict side-by-side. Only the carpeted versions clear the IIC 50 the building code sets between apartments. The report also notes that heavy walking on a wood-framed floor is generally at 100 Hz or less, which the IIC rating does not represent, so a thud can survive a good number. A rug and a dense pad upstairs is the cheapest quiet in the house. Under a hard floor, ask the flooring installer for an acoustic underlayment and its tested IIC on a wood-framed floor. See also basement ceiling insulation.
Home theaters and home offices
A theater is the one room where STC will mislead you. PABCO notes that the STC contour de-emphasizes low frequencies and stops at 125 Hz, which makes it “a much less applicable metric” for media rooms and theaters. Bass is what travels, and a porous absorber barely touches it — BASF’s open cell numbers fall from 0.88 at 500 Hz to 0.22 at 125 Hz. Start with the framing: ROCKWOOL’s catalog tops out its interior wood-stud walls at STC 66, and one of them is a double row of 2x4 studs with a 1-inch gap, 3 inches of stone wool in each row and two layers of 5/8-inch Type X each side. Even that number says nothing below 125 Hz. For a room built around a subwoofer, PABCO’s best-practice list has the next step: consult an acoustician on layout, doors and air handling.
A home office is a different target: speech privacy. On the TSIB table, 40 is the beginning of privacy and 45 is where loud speech stops being noticeable. A filled 2x4 wall with one layer of 5/8-inch Type X (35 in PABCO’s tests) falls short; either resilient channel on one side or a damped board (both covered below) reaches it. The door matters as much: Owens Corning’s QuietZone data sheet calls for solid wood core or insulated metal doors, gasketed at the top and sides, with a threshold closure at the bottom, and advises against sliding doors where noise control matters.
Ducts, outlets and the leaks that undo the job
PABCO shows the same partition at STC 46 properly sealed and STC 36 with a 1/8-inch gap spanning one foot. Ten points, from a gap you could slide a business card into. ASTM C919 calls for a non-hardening sealant in acoustical work, not something that dries hard and cracks.
- Outlets and recessed lights. PABCO says to put electrical and plumbing penetrations in separate stud cavities rather than back to back, and that outlet boxes must be plugged against sound leakage. It calls recessed lights “large open holes in the ceiling,” best treated with a sound isolation box inside the joist cavity. Moving a box is work for an electrician; sealing around it is ours.
- Ducts. A duct running straight from one room into the next is a speaking tube. PABCO advises a main line down a corridor or attic with auxiliary lines to each room, because “the more turns in the ducting, the more difficult it is for sound to find its way through it.” Ductwork is work for an HVAC contractor; we seal the cavities around it.
- The perimeter. PABCO calls sealing the gap at the base of the wall good practice in any sound-rated assembly, with a sealant that stays soft and pliable. On a wall that stays closed it is the same work as air sealing; on new board it is part of hanging the board.
Settle who seals what before work starts, so each part is in one quote — not in two, and not in neither. Sealing inside the cavity — around boxes, pipes, ducts and framing gaps — is part of our insulation work, and so is sealing the outlets and the base of a wall that stays closed. Where new board goes up, the acoustical sealant at its edges and around its cutouts goes on as each sheet is hung, so that bead belongs to the drywall contractor.
Resilient channel, double drywall and mass-loaded vinyl
The other half of the job is drywall and framing work, and it is where the big numbers come from. Decoupling — resilient channel, staggered studs or a double stud wall — breaks the rigid path between the two faces; TSIB says it “can yield an STC rating as high as 63 or more.” It is also the most failure-prone step. PABCO warns that channel failures are common when it goes on upside down or when a finished surface rigidly touches an adjacent one, and its glossary says a short-circuited channel can mean partial or even full failure of the assembly. Mass is a second or heavier layer of board; TSIB notes that doubling a wall’s mass does not automatically double its STC, and in PABCO’s tests a second layer each side was worth 3 points on 16-inch studs and 4 on 24-inch studs. Damped board is a third route: PABCO lists a 2x4 wall with batts and one layer of its QuietRock ES each side at STC 45, against 35 with ordinary Type X. TSIB also names mass-loaded vinyl and liquid-applied damping compound as ways to raise STC, and refers the reader to each manufacturer’s specifications.
Whatever the product, ask the drywall contractor for four things in writing: the tested assembly the quote is based on, with its laboratory report number and test date; the channel product and spacing, installed to the manufacturer’s instructions; the board type and number of layers each side; and acoustical sealant at the edges of the new board and around every cutout in it. A product with no tested assembly that matches your framing has no number you can hold anyone to.
If a wall is being opened anyway, sequence matters: framing and decoupling first, insulation and cavity sealing next, board and its sealant last.
Matching the fix to the noise
Use the TSIB table as the target and pick the assembly that reaches it. The figures are from the tests and the guideline table quoted above.
- Voices next door you can follow. Fill the cavity and seal every gap. Expect roughly 4 to 11 points — a line or two on the TSIB table — not silence.
- Loud speech you want gone (STC 45). In a 2x4 wall, resilient channel on one side (48) or a damped board (45), with the cavity filled.
- Music faintly heard at most (STC 50). Resilient channel on 2x6 studs with 5.5 inches of stone wool (53), or a double stud wall with batts in both rows (56).
- Most sounds impossible to hear (STC 60 and above). A double stud wall with two layers of board each side and insulation in both rows (66), planned together with the doors, ducts and outlets. BASF lists a double wall of that description with foam in only one row at 57.
- Footsteps overhead. Start with the covering on the floor above (IIC 44 with vinyl, 70 with thick carpet and pad on the same floor), then fill the bays, and hang the ceiling on channel if it is coming down anyway.
- Bass. No STC figure describes it below 125 Hz. Bring in an acoustician before choosing the wall.
What soundproofing insulation costs
Most of our projects run between $3,500 and $12,500. On a sound job the insulation price moves with how many walls or bays are involved, whether the cavity is open or has to be dense-packed through drilled holes, the material and its thickness, and how much patching the holes need. Resilient channel, new board and any electrical or duct changes are priced by the trades that do them, so ask each of them to quote against the same tested assembly.
When comparing insulation quotes, check that each one names the material, the thickness, whether the cavity is filled full, and which of the sealing described above it includes; two quotes for “soundproofing insulation” can describe very different jobs. If the project also insulates an exterior wall, an attic or a floor over unheated space, ask whether a state or utility program applies to that part; see New York and New Jersey insulation rebates and Connecticut insulation rebates. The federal 25C tax credit ended for anything placed in service after 31 December 2025. Foam pricing is at spray foam insulation cost.
Common questions about soundproofing insulation
Does insulation soundproof a room?
No. It absorbs sound inside the cavity, which is not the same as blocking it. Filling an empty cavity is worth a handful of STC points: TSIB’s guideline table for metal-stud walls shows batts raising its ranges by 4 to 11, and the American Wood Council’s 2019 report puts them at 7 to 11 in wood floors with a drywall ceiling on resilient channel and no concrete topping. Resilient channel added 13 points to PABCO’s standard 2x4 wall, and a second row of studs added 21.
What is the best insulation for soundproofing?
For an open cavity, a full-thickness mineral wool or fiberglass batt cut to fit with no gaps; TSIB says thickness matters more than density. For a wall already closed, dense-pack cellulose. For a bay crowded with wiring and pipes, open cell spray foam, which BASF rates at an NRC of 0.65. Closed cell foam is not a sound product: BASF measures it at 0.10.
Is mineral wool better than fiberglass for sound?
Not by enough to show up reliably. With 5/8-inch Type X on plain wood studs, current tests put fiberglass at STC 35 (PABCO, 2x4 studs) and ROCKWOOL stone wool at 36 to 38 (2x6 studs). Add resilient channel and the figures are 48 (PABCO’s 2x4 wall) and 53 (ROCKWOOL’s 2x6 wall with 5.5 inches of stone wool), from different laboratories using different channels. Unfaced, both are classified noncombustible under ASTM E136, so choose on fit, handling and price, not on STC.
Does spray foam reduce noise?
Open cell does, in the mid and high frequencies. BASF measures it at an NRC of 0.65 at 3.5 inches under ASTM C423, and lists a 2x4 partition with 5/8-inch Type X each side and 3.5 inches of open cell at STC 34, about what fiberglass does in the same wall, though BASF names no laboratory or test date for that rating. Closed cell measures 0.10, and BASF publishes only “typical” STC values for it, not tested ones.
Will insulation in a basement ceiling help with noise?
It helps with voices, television and music once the ceiling is closed. The American Wood Council’s 2019 report puts the gain from batts at 7 to 11 STC points in a wood floor without a concrete topping, but every floor behind that figure had a drywall ceiling on resilient channel, because the batts work by absorbing sound in the cavity between floor and ceiling. With open joists, fill the bays and then close them, ideally with drywall on resilient channel. For footsteps, the covering on the floor above matters more: on one tested floor it moved the impact rating by 26 points.
How much does soundproofing insulation cost?
Most of our projects run between $3,500 and $12,500. For a sound job the biggest variables are how many walls or bays are involved and whether the cavity is open or has to be dense-packed and patched. Resilient channel and new drywall are a separate drywall contractor’s price.
What is the best soundproofing insulation between floors?
Fill the joist bays with mineral wool or fiberglass, seal every duct, wire and light penetration, and hang the ceiling on resilient channel if it is being rebuilt. Then deal with footsteps from above: on one floor tested for the American Wood Council, thick carpet and pad measured IIC 70 and cushioned vinyl 44.
How do I soundproof a party wall without opening it?
First confirm the wall is yours to change: in a condominium or co-op the association normally owns the walls between units, so ask the board or managing agent in writing what approval is needed. Then dense-pack it: cellulose or fiberglass is blown through small holes until the cavity is firm, and the holes are patched. Dense-pack is one of two ways we fill a finished wall, with injection foam the other, and neither decouples anything, so expect what a filled single-stud wall delivers. Reaching STC 45 or more usually takes drywall work on your side as well.
Why can I still hear my neighbor after adding insulation?
Almost always a leak or a flanking path. PABCO shows the same partition at STC 46 sealed and STC 36 with a 1/8-inch gap spanning one foot. Back-to-back outlet boxes, recessed lights, a duct running straight into the next room, and an unsealed gap at the base of the wall all let sound bypass the wall.
Free estimate and a walk-through
We start by asking what you hear and where you hear it, because the answer decides the method: voices, footsteps and bass are three different problems, and two of them are not solved by anything in a cavity. We look at the framing, which side of the wall you control, and every outlet, light, duct and gap that could leak. If part of the fix is drywall and framing work, you leave with what to ask a drywall contractor for — the channel and its spacing, the board and its layers, the sealant at the new board’s edges and cutouts, and the tested assembly to hold the quote to. For a builder, we price the insulation and cavity sealing against the tested assembly on the drawings.
Call 914-825-6824 or use the contact form, 8am–8pm, seven days. The Home Insulators is family-owned, based in New Rochelle, NY since 2015, with a 100-plus-person in-house crew that never subcontracts. We install mineral wool and fiberglass batts, dense-pack cellulose, injection foam, blown-in fiberglass and open cell spray foam in existing homes and new construction across all of New Jersey, all of Connecticut, New York’s Hudson Valley and Long Island; see our service area.