Ceiling Insulation Weight Tables (All Types Too R Values Covered)

You might think that all insulation tin can be effectively used to insulate an attic. But depending on the material y'all’re using, you lot mightiness non live able to achieve a high enough R-value without installing and so much insulation that your ceiling is inward danger of sagging!

Weight impacts insulation inward surprising ways, and even insulation that seems lightweight tin place risks if installed incorrectly. This is why in that location are industry guidelines for insulation weight.

Rigid foam board is the lightest insulation. Fiberglass in addition to cellulose are mutual together with effective for attics, simply if insulating at R-49 to R-threescore, thicker ceiling boards might be needed. Mineral wool, natural fiber, in addition to spray foam would be likewise heavy at R-49 to R-sixty.

Why Knowing the Weight Is Important

When homeowners accept to homebuilding forums to enquire nearly the weight of insulation, their main business concern is ceiling sagging. If a heavy textile is installed at as well thick of a depth, it can set pressure on the drywall ceiling boards and effort them to sag.

Sagging tin eventually effort the ceiling boards to autumn, and then it absolutely needs to live addressed together with, ideally, prevented inwards the commencement place. You need to know the weight of your insulation to make sure that your drywall ceiling can handle it.

While this article is mostly virtually ceiling insulation, yous should bill that insulation weight is as well pertinent to walls.

Insulation that is also heavy can sag within wall cavities. It needs to stay vertical together with snug inside the wall to live upward to its R-value.

If it sags under its own weight, the insulation volition get out large gaps towards the peak of the wall. Air will act through these gaps as well as transfer rut, undermining the efficacy of the insulation.

Fiberglass

Loose-Fill

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness inwards ft	thickness inwards inches	weight (lbs/ft^ii)	r-value	thickness inward ft	thickness inwards inches	weight (lbs/ft^2)	r-value	thickness inward ft	thickness in inches	weight (lbs/ft^ii)
three	0.0670	0.8041	0.0402	3	0.1149	ane.3784	0.2295	three	0.0909	one.0913	0.1181
four	0.0893	one.0722	0.0535	4	0.1532	i.8379	0.3060	iv	0.1213	ane.4550	0.1574
five	0.1117	i.3402	0.0669	five	0.1914	two.2974	0.3825	v	0.1516	ane.8188	0.1968
vi	0.1340	ane.6083	0.0803	vi	0.2297	two.7568	0.4589	6	0.1819	two.1826	0.2362
8	0.1787	ii.1444	0.1071	8	0.3063	3.6758	0.6119	eight	0.2425	2.9101	0.3149
x	0.2234	2.6805	0.1339	ten	0.3829	4.5947	0.7649	10	0.3031	3.6376	0.3936
thirteen	0.2904	iii.4846	0.1740	thirteen	0.4978	five.9731	0.9944	thirteen	0.3941	iv.7289	0.5117
xv	0.3351	four.0207	0.2008	fifteen	0.5743	vi.8921	i.1474	xv	0.4547	5.4564	0.5904
17	0.3797	4.5568	0.2276	17	0.6509	seven.8110	i.3003	17	0.5153	half-dozen.1839	0.6692
nineteen	0.4244	v.0929	0.2544	19	0.7275	viii.7300	1.4533	nineteen	0.5760	6.9114	0.7479
xx	0.4467	v.3609	0.2677	twenty	0.7658	ix.1894	ane.5298	20	0.6063	vii.2752	0.7872
21	0.4691	v.6290	0.2811	21	0.8041	nine.6489	ane.6063	21	0.6366	vii.6389	0.8266
thirty	0.6701	viii.0414	0.4016	30	i.1487	13.7842	2.2947	thirty	0.9094	x.9128	one.1809
38	0.8488	ten.1858	0.5087	38	i.4550	17.4599	two.9066	38	i.1519	13.8229	one.4957
49	1.0945	thirteen.1343	0.6560	49	i.8762	22.5141	iii.7480	49	i.4854	17.8242	i.9287
60	ane.3402	sixteen.0828	0.8032	60	ii.2974	27.5683	iv.5894	sixty	i.8188	21.8256	2.3617

Batt

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness inward ft	thickness inward inches	weight (lbs/ft^2)	r-value	thickness inwards ft	thickness in inches	weight (lbs/ft^ii)	r-value	thickness inwards ft	thickness inwards inches	weight (lbs/ft^two)
three	0.0705	0.8455	0.0211	iii	0.0861	i.0338	0.1721	three	0.0783	0.9397	0.0899
four	0.0939	ane.1274	0.0282	iv	0.1149	1.3783	0.2295	4	0.1044	ane.2529	0.1199
five	0.1174	i.4092	0.0352	five	0.1436	one.7229	0.2868	five	0.1305	one.5661	0.1499
half dozen	0.1409	ane.6911	0.0422	6	0.1723	two.0675	0.3442	half dozen	0.1566	i.8793	0.1799
viii	0.1879	two.2548	0.0563	8	0.2297	2.7567	0.4589	viii	0.2088	2.5057	0.2399
x	0.2349	2.8185	0.0704	ten	0.2872	three.4459	0.5736	x	0.2610	three.1322	0.2998
xiii	0.3053	iii.6640	0.0915	thirteen	0.3733	four.4796	0.7457	xiii	0.3393	4.0718	0.3898
15	0.3523	4.2277	0.1056	15	0.4307	five.1688	0.8605	15	0.3915	four.6983	0.4497
17	0.3993	4.7914	0.1196	17	0.4882	v.8579	0.9752	17	0.4437	5.3247	0.5097
19	0.4463	5.3551	0.1337	nineteen	0.5456	six.5471	1.0899	19	0.4959	5.9511	0.5697
xx	0.4697	5.6370	0.1408	xx	0.5743	vi.8917	ane.1473	20	0.5220	vi.2643	0.5996
21	0.4932	v.9188	0.1478	21	0.6030	vii.2363	one.2047	21	0.5481	half-dozen.5776	0.6296
thirty	0.7046	eight.4555	0.2111	thirty	0.8615	ten.3376	1.7209	thirty	0.7830	ix.3965	0.8995
38	0.8925	10.7102	0.2674	38	one.0912	thirteen.0942	ii.1799	38	0.9919	11.9022	1.1393
49	one.1509	thirteen.8106	0.3449	49	one.4071	16.8847	two.8109	49	one.2790	xv.3476	1.4691
lx	1.4092	sixteen.9109	0.4223	lx	1.7229	20.6751	3.4419	sixty	ane.5661	18.7930	i.7989

Explaining the Tables

Overall, fiberglass is i of the lightest insulating material (the other is rigid foam board). Fiberglass is used inwards all sorts of products because it is extremely potent withal lightweight.

The fluffy pinkish fiberglass y'all encounter used every bit insulation is made by spinning drinking glass-wool fibers. The raw material are recycled drinking glass as well as sand. Streams of glass are created through holes inward a rotating spinner as well as chopped up into tiny strands.

In improver to the inherent low-cal weight of fiberglass equally a cloth, fiberglass insulation is peculiarly calorie-free because it is less dense than, order, cellulose. Think of the cotton fiber candy-similar construction of fiberglass compared to the denser, somewhat clunkier shredded newspaper that makes upwards cellulose.

It does not take the highest inherent R-value, then yous postulate thicker layers of fiberglass batts to attain the same R-value that foam board or mineral wool, for instance, could achieve alongside thinner layers.

The density of liberate-fill fiberglass depends on how much is packed into the space (although compression should live avoided).

Fiberglass is expected to settle, though not every bit much equally cellulose insulation since cellulose is denser. A professional person installer volition have settling into business relationship when determining the thickness.

Fiberglass batts come up inward different densities, with higher-density batts having higher R-values as well as higher prices.

Despite the lightweight nature of fiberglass, yous could function into around issues alongside weight if yous’re trying to achieve high R-values.

For case, the Department of Energy’s recommendation for attics is R-38 to R-sixty for most parts of the United States, with R-49 to R-sixty recommended for states in the Northwest, Upper Midwest, Northern Plains, too Pacific Northwest.

Achieving R-49 amongst fiberglass batts could hateful putting over xv inches of insulation inwards your ceiling, which would take a weight of ane.47 lbs per foursquare foot.

The United Statesgrand. Corporation, which is a leading drywall manufacturer, has set maximum weight guidelines for drywall:

Installation of drywall	Maximum weight of insulation to a higher place drywall
ane/ii inches drywall on joists spaced 24 inches on heart	1.3 lbs/ft^two
v/8 inches drywall on joists spaced 24 inches on middle	ii.ii lbs/ft^2
one/ii inches drywall on joists spaced 16 inches on middle	ii.4 lbs/ft^2

To follow manufacturer recommendations when insulating to R-49 to R-lx alongside fiberglass batts, yous would desire to go above in addition to beyond the basic drywall dimensions (½” drywall on 24” joists) to ensure that your ceiling doesn’t sag.

[Replace amongst licensed image; joist spacing case]

Loose-make full fiberglass would live heavier, requiring simply over 17 inches too one.92 lbs per square foot to attain R-49. Loose-fill needs to live thicker because it will settle over fourth dimension, whereas batts are more than structured in addition to stable.

You don’t take to worry most the weight of fiberglass inwards walls. A criterion ii×4 wall entirely needs to accomplish R-13 to R-15, which would weigh less than 0.five lbs per foursquare pes.

Cellulose

Used Average Thermal Conductivity
r-value	thickness inwards ft	thickness in inches	weight (lbs/ft^two)
three	0.0711	0.8528	0.1331
iv	0.0948	one.1371	0.1775
five	0.1184	i.4214	0.2218
six	0.1421	i.7056	0.2662
8	0.1895	ii.2742	0.3549
ten	0.2369	two.8427	0.4437
xiii	0.3080	iii.6955	0.5768
fifteen	0.3553	iv.2641	0.6655
17	0.4027	four.8326	0.7542
19	0.4501	5.4012	0.8430
20	0.4738	five.6854	0.8873
21	0.4975	5.9697	0.9317
thirty	0.7107	8.5282	one.3310
38	0.9002	ten.8023	1.6859
49	one.1608	xiii.9293	ii.1739
lx	i.4214	17.0563	2.6620

Explaining the Table

Cellulose is paper-based, made from recycled woods, paper, together with cardboard. These material are less fine than fiberglass strands, so cellulose is denser.

Because cellulose is organic together with combustible, it must live extensively treated amongst burn-retardant chemicals. These fire retardants add weight. By contrast, fiberglass does not necessitate to live treated.

Cellulose also settles significantly, and so it will end upwards denser than fiberglass. With free-make full insulation (cellulose or blown-inwards fiberglass), yous can pack a lot into a minor space. Be careful, because overfilling volition position force per unit area on the drywall.

Compared to fiberglass, cellulose carries a greater adventure of drywall sagging. Let’sec await dorsum at the USthousand. Corporation’sec guidelines about maximum insulation weight:

Installation of drywall	Maximum weight of insulation above drywall
one/ii inches drywall on joists spaced 24 inches on eye	i.3 lbs/ft^ii
five/viii inches drywall on joists spaced 24 inches on eye	ii.ii lbs/ft^two
ane/2 inches drywall on joists spaced 16 inches on middle	2.four lbs/ft^ii

To attain R-49 to R-threescore, y'all’d typically require xiii-17 inches of cellulose insulation. This would weigh 2.i-ii.half dozen lbs per square human foot. Manufacturers enjoin that drywall can withstand 2.ii-ii.4 lbs per square foot nether certain circumstances (thicker drywall, closer joists).

There is a lot of argue about the United States of America1000. Corporation’s guidelines. Many light-green builders insulate attic floors at fifty-fifty higher R-values than required, going upwardly to R-70 or even R-100. Cellulose at R-100 would mean more than than 2 feet of cellulose, which past far exceeds manufacturer recommendations.

Yet, professional contractors on Green Building Advisor forums note that they routinely ignore these recommendations. But despite anecdotal success stories, recall that ignoring United Statesthousand.’s nautical chart could plant a code violation as you are required to follow the manufacturer’sec instructions.

Tip: beware of wet. Cellulose holds more than wet than fiberglass, as organic materials absorb water spell fiberglass strands do non. Condensation or water leaks tin can make cellulose much heavier than expected. Furthermore, when the newspaper facing of drywall gets wet, it tin can kickoff to sag.

Mineral Wool

Loose-Fill

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^two)	r-value	thickness inward ft	thickness inward inches	weight (lbs/ft^2)	r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^ii)
three	0.0621	0.7447	0.3990	three	0.0676	0.8112	0.2448	three	0.0648	0.7779	0.3258
4	0.0827	0.9929	0.5320	four	0.0901	i.0816	0.3264	4	0.0864	ane.0372	0.4344
v	0.1034	one.2411	0.6650	five	0.1127	ane.3520	0.4080	5	0.1080	1.2966	0.5430
half-dozen	0.1241	1.4893	0.7980	half-dozen	0.1352	ane.6224	0.4895	six	0.1297	1.5559	0.6516
8	0.1655	one.9857	one.0640	eight	0.1803	two.1632	0.6527	viii	0.1729	two.0745	0.8688
10	0.2068	2.4822	i.3301	10	0.2253	2.7041	0.8159	10	0.2161	2.5931	ane.0860
thirteen	0.2689	3.2268	i.7291	13	0.2929	iii.5153	1.0607	xiii	0.2809	3.3711	i.4118
xv	0.3103	iii.7233	1.9951	xv	0.3380	four.0561	i.2239	xv	0.3241	3.8897	ane.6289
17	0.3516	four.2197	2.2611	17	0.3831	four.5969	ane.3870	17	0.3674	four.4083	one.8461
19	0.3930	4.7161	two.5271	19	0.4281	five.1377	ane.5502	19	0.4106	4.9269	ii.0633
20	0.4137	4.9644	ii.6601	twenty	0.4507	5.4081	one.6318	twenty	0.4322	5.1862	ii.1719
21	0.4344	5.2126	two.7931	21	0.4732	5.6785	1.7134	21	0.4538	five.4455	two.2805
thirty	0.6205	vii.4465	iii.9902	30	0.6760	eight.1122	two.4477	xxx	0.6483	7.7794	3.2579
38	0.7860	9.4323	five.0542	38	0.8563	10.2754	three.1004	38	0.8212	9.8539	four.1267
49	i.0136	12.1627	6.5173	49	1.1042	13.2499	3.9979	49	ane.0589	12.7063	5.3212
lx	one.2411	xiv.8931	seven.9803	threescore	1.3520	sixteen.2243	iv.8954	lx	one.2966	15.5587	half-dozen.5158

Batt

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness in ft	thickness in inches	weight (lbs/ft^two)	r-value	thickness inward ft	thickness in inches	weight (lbs/ft^ii)	r-value	thickness inward ft	thickness in inches	weight (lbs/ft^2)
iii	0.0607	0.7280	0.0189	three	0.1231	ane.4768	0.3841	iii	0.0919	ane.1024	0.1577
4	0.0809	0.9707	0.0252	iv	0.1641	ane.9691	0.5122	four	0.1225	ane.4699	0.2103
v	0.1011	1.2134	0.0316	5	0.2051	2.4614	0.6402	5	0.1531	ane.8374	0.2629
six	0.1213	one.4560	0.0379	vi	0.2461	two.9537	0.7683	half dozen	0.1837	two.2048	0.3154
eight	0.1618	one.9414	0.0505	8	0.3282	three.9382	one.0244	viii	0.2450	2.9398	0.4206
ten	0.2022	ii.4267	0.0631	x	0.4102	iv.9228	one.2805	x	0.3062	three.6747	0.5257
thirteen	0.2629	3.1547	0.0821	thirteen	0.5333	half-dozen.3996	1.6646	xiii	0.3981	four.7772	0.6834
fifteen	0.3033	3.6401	0.0947	15	0.6153	vii.3841	ane.9207	15	0.4593	five.5121	0.7886
17	0.3438	four.1254	0.1073	17	0.6974	viii.3687	two.1768	17	0.5206	half-dozen.2471	0.8937
xix	0.3842	4.6108	0.1199	xix	0.7794	ix.3533	2.4329	xix	0.5818	vi.9820	0.9989
twenty	0.4045	four.8534	0.1262	twenty	0.8205	nine.8455	two.5610	20	0.6125	7.3495	1.0514
21	0.4247	5.0961	0.1326	21	0.8615	x.3378	2.6890	21	0.6431	seven.7170	i.1040
xxx	0.6067	vii.2801	0.1894	xxx	one.2307	14.7683	iii.8415	30	0.9187	eleven.0242	1.5772
38	0.7685	9.2215	0.2399	38	one.5589	xviii.7065	4.8659	38	ane.1637	thirteen.9640	one.9977
49	0.9909	eleven.8909	0.3093	49	2.0101	24.1216	six.2744	49	1.5005	18.0062	two.5760
lx	one.2134	fourteen.5603	0.3787	lx	two.4614	29.5366	7.6829	60	i.8374	22.0484	three.1543

Explaining the Tables

Mineral wool, also called stone wool or rockwool, is an insulation made from fibers of mineral materials. Materials such every bit slag as well as ceramics are spun into extremely thin fibers that are layered together to create a squishy fabric resembling fiberglass.

But spell mineral wool mightiness simply wait similar brown/yellow fiberglass, it is real dissimilar.

First of all, mineral wool is much denser than fiberglass or cellulose. Mineral wool batts are then dense that y'all tin grade a batt just past pressing the edge of a tape measure into the surface to brand an indentation.

[Replace with licensed ikon: example of texture/density] 

Mineral wool is designed to live denser for several reasons:

• Firstly, that density allows mineral wool to attain a higher R-value per inch than fiberglass.





• Secondly, the dense, stiff batts are slow to install. They “cutting like breadstuff” too do not fall apart or fall downwards, fifty-fifty if installed in between ceiling joists without back up.





• Thirdly, mineral wool is marketed equally a slap-up soundproofing textile because of its density.

But that extra density too has its downsides. Because mineral wool has more fabric packed into each square inch, it is ane of the more than expensive insulation options out in that location.

Most importantly, the density of mineral wool contributes to it weighing more than than fiberglass or cellulose. The mineral material weigh more than drinking glass or paper inwards the offset place, in addition to the dense packing adds to that weight.

Mineral wool is less usually used inwards attics because its weight tin live prohibitive.

If installed to R-49 to R-sixty, unloosen-fill mineral wool would weigh v.3-6.five lbs per foursquare pes as well as mineral wool batts would weigh two.five-three.ii lbs per square human foot—both style over the StatesK.’sec upper bound of ii.4 lbs per foursquare pes.

Mineral wool is about pop for purpose inwards exterior walls, equally wall cavities accept limited infinite too only three.five inches of roughly mineral wool batts tin get y'all to R-xv. The required R-values for walls are besides lower.

Tip: When insulating walls, in that location’second a boundary on thickness in addition to non much of a limit on weight. When insulating unfinished attics, there’s a limit on weight too non much of a limit on thickness.

Natural Fiber

Loose-Fill

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^two)	r-value	thickness inwards ft	thickness inwards inches	weight (lbs/ft^ii)	r-value	thickness inwards ft	thickness in inches	weight (lbs/ft^two)
three	0.0693	0.8320	0.1082	iii	0.0849	one.0192	0.5302	iii	0.0771	0.9256	0.3010
4	0.0924	one.1094	0.1443	four	0.1132	ane.3590	0.7070	iv	0.1028	ane.2342	0.4013
five	0.1156	one.3867	0.1804	5	0.1416	ane.6987	0.8837	5	0.1286	one.5427	0.5016
6	0.1387	ane.6640	0.2164	6	0.1699	2.0384	one.0605	six	0.1543	i.8512	0.6019
8	0.1849	ii.2187	0.2886	8	0.2265	ii.7179	one.4140	eight	0.2057	ii.4683	0.8026
x	0.2311	ii.7734	0.3607	10	0.2831	three.3974	ane.7674	10	0.2571	3.0854	1.0032
xiii	0.3005	iii.6054	0.4689	xiii	0.3681	four.4166	two.2977	thirteen	0.3343	four.0110	ane.3042
xv	0.3467	4.1601	0.5411	xv	0.4247	five.0961	two.6512	fifteen	0.3857	four.6281	i.5048
17	0.3929	four.7148	0.6132	17	0.4813	v.7756	three.0046	17	0.4371	v.2452	one.7054
nineteen	0.4391	5.2694	0.6853	nineteen	0.5379	half dozen.4551	three.3581	nineteen	0.4885	5.8623	i.9061
20	0.4622	five.5468	0.7214	twenty	0.5662	half dozen.7948	iii.5349	xx	0.5142	6.1708	2.0064
21	0.4853	five.8241	0.7575	21	0.5945	seven.1345	3.7116	21	0.5399	6.4793	two.1067
xxx	0.6933	8.3202	1.0821	xxx	0.8494	x.1922	v.3023	30	0.7713	ix.2562	iii.0096
38	0.8782	x.5389	1.3707	38	ane.0758	12.9101	vi.7163	38	0.9770	xi.7245	3.8122
49	i.1325	13.5896	one.7674	49	one.3873	16.6473	eight.6604	49	1.2599	fifteen.1184	iv.9157
lx	1.3867	sixteen.6403	ii.1642	sixty	one.6987	xx.3844	x.6046	lx	one.5427	eighteen.5124	half-dozen.0192

Batt

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness inward ft	thickness inward inches	weight (lbs/ft^two)	r-value	thickness in ft	thickness in inches	weight (lbs/ft^ii)	r-value	thickness inwards ft	thickness inwards inches	weight (lbs/ft^ii)
iii	0.0763	0.9152	0.0238	3	0.1629	ane.9552	0.5086	iii	0.1196	ane.4352	0.2053
iv	0.1017	one.2203	0.0317	4	0.2172	2.6070	0.6781	iv	0.1595	i.9136	0.2738
five	0.1271	i.5254	0.0397	five	0.2716	3.2587	0.8476	5	0.1993	ii.3920	0.3422
half dozen	0.1525	ane.8304	0.0476	six	0.3259	3.9105	one.0172	6	0.2392	ii.8705	0.4107
8	0.2034	ii.4406	0.0635	8	0.4345	v.2140	i.3562	8	0.3189	three.8273	0.5475
x	0.2542	iii.0507	0.0794	ten	0.5431	half-dozen.5175	ane.6953	10	0.3987	iv.7841	0.6844
thirteen	0.3305	three.9659	0.1032	xiii	0.7061	eight.4727	ii.2039	thirteen	0.5183	vi.2193	0.8898
xv	0.3813	4.5761	0.1190	15	0.8147	ix.7762	ii.5429	fifteen	0.5980	seven.1761	1.0266
17	0.4322	5.1862	0.1349	17	0.9233	eleven.0797	2.8820	17	0.6777	eight.1330	one.1635
19	0.4830	five.7964	0.1508	nineteen	one.0319	12.3832	iii.2211	nineteen	0.7575	9.0898	i.3004
20	0.5085	vi.1015	0.1587	20	1.0862	thirteen.0349	iii.3906	xx	0.7973	9.5682	one.3689
21	0.5339	vi.4065	0.1666	21	one.1406	thirteen.6867	three.5601	21	0.8372	x.0466	1.4373
xxx	0.7627	ix.1522	0.2381	xxx	one.6294	nineteen.5524	5.0859	30	ane.1960	fourteen.3523	ii.0533
38	0.9661	11.5928	0.3015	38	2.0639	24.7664	half-dozen.4421	38	one.5150	18.1796	2.6008
49	ane.2457	14.9486	0.3888	49	ii.6613	31.9356	eight.3070	49	ane.9535	23.4421	three.3537
60	i.5254	18.3044	0.4761	60	iii.2587	39.1048	ten.1718	lx	2.3920	28.7046	iv.1066

Explaining the Tables

Natural fiber insulation tin can include sheep’sec wool, cotton wool fibers, as well as/or hemp fibers. These organic material are heavier than fiberglass together with fifty-fifty cellulose, in addition to most every bit dense in addition to heavy equally mineral wool.

Now, it seems similar wool together with cotton would live lighter than stone-based materials, merely mean of your thickest wool coat or sweater. Those things tin can be heavy!

In add-on, natural fiber insulation needs to live installed at a greater thickness than cellulose, fiberglass, or mineral wool to reach the R-values necessary for attic insulation. Natural fiber batts take to be installed at 23-28 inches thick for R-49 to R-threescore, whereas cellulose needs to live 13-eighteen inches thick.

Because of the postulate for more than layers besides every bit the difference in textile, natural fiber rated at R-49 weighs more than cellulose rated at R-49.

As amongst fiberglass and mineral wool, natural fiber insulation inward unloose-fill form tends to weigh more than (at a given rating) than natural fiber inward batt course.

This is partly because it becomes denser: liberate-fill up is installed to account for settling, and so 15 inches of free-make full (settled) was likely thicker when beginning installed.

For both liberate-fill up together with batts, natural fiber insulation volition weigh more than the USAgrand’s maximum weight guidelines (one.3-2.iv lbs per square pes) for drywall ceilings. It’s best to function natural fiber insulation inwards walls rather than ceilings.

You could too wait into combining natural fiber insulation with a layer of foam board, for case, to cut down the sum of natural fiber yous need to role to achieve attic R-values.

Plastic Fiber

Used Average Thermal Conductivity
r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^ii)
iii	0.0433	0.5200	0.0947
four	0.0000	0.0000	0.0000
5	0.0000	0.0000	0.0000
half-dozen	0.0000	0.0000	0.0000
viii	0.0000	0.0000	0.0000
10	0.0000	0.0000	0.0000
13	0.0000	0.0000	0.0000
fifteen	0.0000	0.0000	0.0000
17	0.0000	0.0000	0.0000
xix	0.0000	0.0000	0.0000
twenty	0.0000	0.0000	0.0000
21	0.0000	0.0000	0.0000
xxx	0.0000	0.0000	0.0000
38	0.0000	0.0000	0.0000
49	0.0000	0.0000	0.0000
lx	0.0000	0.0000	0.0000

Explaining the Table

Plastic fiber insulation is made out of recycled plastic milk bottles—a type of plastic called polyethylene terephthalate or PET.

It is difficult to generalize most the weight as well as thickness of plastic fiber insulation because it comes inward and then many different forms: thin blanket sheets, thick fluffy batts, in addition to spray. Additionally, it’second the to the lowest degree mutual grade of insulation on this listing.

Plastic fiber insulation is fairly comparable to fiberglass in its weight as well as efficacy. When installed to an R-value of iii, plastic fiber insulation typically weighs 0.0947 lbs per square human foot patch fiberglass batts weigh 0.0899 lbs per foursquare foot in addition to cellulose weighs 0.1331 lbs per foursquare foot.

It makes sense that plastic fiber insulation would weigh slightly more than fiberglass, because the plastic is flammable and needs to be treated amongst burn retardants which contributes to the weight.

While uncommon, nearly forms of plastic fiber insulation should non live likewise heavy for attic function, only it’sec important to cheque your detail production and inquire a professional contractor.

Spray Foam

Used Minimum Thermal Conductivity	Used Maximum Thermal Conductivity	Used Average Thermal Conductivity
r-value	thickness inwards ft	thickness inward inches	weight (lbs/ft^two)	r-value	thickness inwards ft	thickness in inches	weight (lbs/ft^ii)	r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^two)
3	0.0693	0.8320	0.1082	3	0.0849	i.0192	0.5302	iii	0.0771	0.9256	0.3010
four	0.0924	1.1094	0.1443	4	0.1132	ane.3590	0.7070	4	0.1028	ane.2342	0.4013
five	0.1156	1.3867	0.1804	five	0.1416	i.6987	0.8837	five	0.1286	one.5427	0.5016
vi	0.1387	1.6640	0.2164	vi	0.1699	ii.0384	i.0605	half-dozen	0.1543	ane.8512	0.6019
eight	0.1849	2.2187	0.2886	viii	0.2265	ii.7179	one.4140	8	0.2057	ii.4683	0.8026
x	0.2311	ii.7734	0.3607	x	0.2831	3.3974	i.7674	ten	0.2571	3.0854	ane.0032
13	0.3005	three.6054	0.4689	thirteen	0.3681	4.4166	two.2977	13	0.3343	4.0110	ane.3042
fifteen	0.3467	four.1601	0.5411	xv	0.4247	5.0961	ii.6512	fifteen	0.3857	4.6281	ane.5048
17	0.3929	iv.7148	0.6132	17	0.4813	5.7756	3.0046	17	0.4371	5.2452	1.7054
nineteen	0.4391	5.2694	0.6853	19	0.5379	6.4551	3.3581	xix	0.4885	five.8623	1.9061
20	0.4622	five.5468	0.7214	twenty	0.5662	vi.7948	3.5349	twenty	0.5142	vi.1708	2.0064
21	0.4853	five.8241	0.7575	21	0.5945	vii.1345	3.7116	21	0.5399	half dozen.4793	2.1067
30	0.6933	viii.3202	1.0821	xxx	0.8494	ten.1922	5.3023	thirty	0.7713	nine.2562	iii.0096
38	0.8782	ten.5389	1.3707	38	one.0758	12.9101	half dozen.7163	38	0.9770	eleven.7245	3.8122
49	ane.1325	thirteen.5896	i.7674	49	1.3873	sixteen.6473	8.6604	49	ane.2599	fifteen.1184	iv.9157
sixty	one.3867	sixteen.6403	two.1642	sixty	i.6987	xx.3844	ten.6046	lx	i.5427	xviii.5124	half dozen.0192

Explaining the Tables

Spray foam is made of foam plastics and is much denser than batts or unloose-fill up insulation, reaching high R-values at low thicknesses. But fifty-fifty at low thicknesses, spray foam is heavy.

In particular, high-density too medium-density spray foams tend to live heavy because they are shut-prison cell foam (they have a denser construction). Low-density spray foam is open up-cell. Only medium- too low-density spray foam are used for interior attic insulation.

These tables suggest that approximately spray foams tin live prohibitively heavy for attic floors if layered more than vii inches thick.

When installed to an R-value of xxx, spray foam needs to be about ix inches thick in addition to volition weigh over three lbs per foursquare foot. This exceeds the the Statesthou Corporation’s guidelines for what drywall tin grip.

But insulation contractors however function spray form on attic floors, oftentimes in conjunction alongside other types of insulation to reach those higher R-values without too much weight. It’second really mutual to purpose spray foam to seal around fiberglass batts, for example.

Additionally, people frequently spray the rafters straight, rather than the floor. Spray foam allows y'all to do this because it is and then adhesive. It too has around structural integrity, every bit it dries difficult and won’t slip downwards the slanted rafters. That way, yous don’t fifty-fifty have to worry well-nigh your ceiling drywall.

If you lot role spray foam to insulate walls, be certain that you lot scrape down excess foam to make a polish surface before installing the drywall. Failing to trim down the foam can lay pressure level on the drywall.

Rigid Foam Boards

Used Average Thermal Conductivity
r-value	thickness in ft	thickness inwards inches	weight (lbs/ft^2)
3	0.0503	0.6032	0.0653
4	0.0670	0.8043	0.0870
five	0.0838	ane.0054	0.1088
six	0.1005	i.2064	0.1305
viii	0.1340	one.6086	0.1741
10	0.1676	two.0107	0.2176
13	0.2178	ii.6139	0.2828
xv	0.2513	three.0161	0.3264
17	0.2849	3.4182	0.3699
19	0.3184	three.8203	0.4134
20	0.3351	iv.0214	0.4352
21	0.3519	four.2225	0.4569
xxx	0.5027	half dozen.0321	0.6527
38	0.6367	vii.6407	0.8268
49	0.8210	nine.8525	ane.0661
lx	ane.0054	12.0642	ane.3055

Explaining the Tables

Rigid foam boards are the near lightweight insulation pick available. Foam boards are the best fashion to reach R-threescore without exceeding U.S.A.M.’sec weight limits for criterion drywall ceilings (½ inch drywall alongside joists spaced 24 inches on eye).

Foam boards pack a lot of R-value into a thin together with calorie-free package. Compared to a human foot together with a half of cellulose or fiberglass, y'all tin can function only a human foot of foam board to reach R-60.

So why is spray foam and so much heavier than rigid foam boards, if they’re both made of foam?

Spray foam is designed to live a improve insulator than foam boards, equally it is used to seal cracks too create airtight bonds. Spray foam is more than expensive than rigid foam board because it is denser together with has a higher inherent R-value.

Additionally, spray foam as well as foam boards are made from unlike types of foam plastics.

Spray foam is polyurethane or polyisocyanurate. Rigid foam board is polystyrene, which is cheaper, lighter, in addition to has less thermal resistance than polyurethane. Polyurethane has more than structural rigidity.

But that doesn’t hateful that spray foam is ameliorate than rigid foam boards!

As nosotros accept seen, spray foam is problematically heavy for role on attic floors. Rigid foam board is highly versatile because it is thin, lite, and effective. If you lot’re using foam board, you actually don’t postulate to worry most drywall sagging.

Sources

​​https://homeguides.sfgate.com/cook-sagging-drywall-ceilings-42297.html 

https://cen.acs.org/materials/inorganic-chemical science/sec-fiberglass-does-frail-material/96/i38

https://www.forbes.com/home-improvement/insulation/what-is-fiberglass-insulation/

https://www.greenbuildingadvisor.com/article/will-thick-cellulose-drive-your-ceiling-to-sag

https://www.jm.com/en/blog/2021/march/head-to-head–mineral-wool-vs–fiberglass-/

https://www.dbsg.com/weblog/this-vs-that-spray-foam-or-rigid-foam-insulation/